Shift power transmission apparatus and travel power transmission device

ABSTRACT

Disclosed is a shift power transmission apparatus for readily suppressing or avoiding size increase thereof. The apparatus includes an input shaft (22) receiving engine drive force, a hydraulic continuously variable transmission (30) driven by the input shaft (22), a planetary power transmission section (40) combining drive force from the input shaft (22) and output from the hydraulic continuously variable transmission (30) for outputting the combined drive force, and an output rotary member (24) outputting power to a travel apparatus. The planetary power transmission section (40) and the output rotary member (24) are arranged on a side of the hydraulic continuously variable transmission (30) associated with an engine-coupled side of the input shaft (22). The drive force is inputted to the planetary power transmission section (40) from a portion between the engine-coupled side and the hydraulic continuously variable transmission-coupled side of the input shaft (22).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/001,713, filed Jan. 20, 2016, which is a division of U.S. applicationSer. No. 14/007,775 filed Mar. 27, 2012, now U.S. Pat. No. 9,261,182,which is the United States national phase of International ApplicationNo. PCT/JP2012/057983 filed Mar. 27, 2012 and claims priority toJapanese Patent Application Nos. 2011-078544 and 2011-078545, both filedMar. 31, 2011 and 2011-176198 and 2011-176200, both filed Aug. 11, 2011,the disclosures of which are each hereby incorporated in their entiretyby reference

TECHNICAL FIELD

The present invention relates to a shift power transmission apparatusand a travel power transmission apparatus. More specifically, thepresent invention relates to, but is not limited to, a shift powertransmission apparatus and a travel power transmission apparatus in anagricultural apparatus.

BACKGROUND ART

[1] A shift power transmission apparatus is provided with an input shaftthat receives engine drive force, a hydraulic continuously variabletransmission that is driven by the input shaft, a planetary powertransmission section that combines drive force from the input shaft andoutput from the hydraulic continuously variable transmission and outputsthe combined drive force, and an output rotary member that outputs powerto a travel apparatus.

Patent Document 1 describes a conventional example of a shift powertransmission apparatus. The shift power transmission apparatus describedin Patent Document 1 includes a pump shaft that passes through ahydraulic pump in a continuously variable shift section (hydrauliccontinuously variable transmission), and is configured such that driveforce from the engine is inputted to the pump shaft on one sideprotruding from the continuously variable transmission, drive force fromthe pump shaft is transmitted from the other side of the pump shaftprotruding from the continuously variable shift section to a compoundplanetary power transmission section, the continuously variable shiftsection is driven by the engine drive force, and the engine drive forceand the output from the continuously variable shift section are combinedby the compound planetary power transmission section.

[2] On the other hand, in a shift power transmission apparatus describedin Patent Document 2, a power transmission system for transmittingoutput from the engine to front/rear wheels is provided with a hydrauliccontinuously variable shift apparatus (hydraulic continuously variabletransmission), a planetary gear mechanism (planetary power transmissionsection), and two hydraulic clutches. When an HST (Hydraulic StaticTransmission) mode drive train (HST mode power transmission) isconfigured by one of the two hydraulic clutches being connected, outputfrom the engine is transmitted to front/back wheels after beingsubjected to speed change by the hydraulic continuously variable shiftapparatus. When an HMT (Hydraulic Mechanical Transmission) mode drivetrain (HMT mode power transmission) is configured the other one of thetwo hydraulic clutches being connected, output from the hydrauliccontinuously variable shift apparatus is inputted to the planetary gearapparatus, the planetary gear apparatus combines output from the enginewith output from the hydraulic continuously variable shift apparatus andoutputs the combined drive force, and the combined drive force istransmitted to front/rear wheels.

Also, in the shift power transmission apparatus described inaforementioned Patent Document 1, a power transmission system thattransmits output from the engine to a front wheel differential mechanismand a rear wheel differential mechanism is provided with a continuouslyvariable shift section (hydraulic continuously variable transmission), aplanetary power transmission section, and a forward/reverse switchingapparatus. Output from the engine is inputted to the continuouslyvariable shift section and the planetary power transmission section, anda planetary gear apparatus combines the output from the engine withoutput from the hydraulic continuously variable shift apparatus. Thecombined drive force outputted by the planetary gear apparatus isinputted to the forward/reverse switching apparatus and converted intoforward drive force and reverse drive force, which is then transmittedto the front wheel differential mechanism and the rear wheeldifferential mechanism.

[3] There is a travel power transmission apparatus that includes a shiftpower transmission device. The shift power transmission device has ahydrostatic continuously variable shift section that operates so as toreceive drive force from an engine and subject it to speed change, thespeed-changed drive force to be output being subjected to speed changealong an HST shift line, and a planetary power transmission section thatoperates so as to receive and combine the drive force from the engineand the speed-changed drive force from the continuously variable shiftsection, the combined drive force to be output being subjected to speedchange along an HMT shift line by the speed change performed by thecontinuously variable shift section. The shift power transmission deviceis provided with a clutch mechanism that can be switched between an HSTsetting state, which is for setting HST power transmission in which thespeed-changed drive force output from the continuously variable shiftsection is outputted to a travel apparatus, and an HMT setting state,which is for setting HMT power transmission in which the combined driveforce output from the planetary power transmission section is outputtedto the travel apparatus. The travel power transmission apparatus alsoincludes a shift control module for, based on a shift instruction from ashift operation device, controlling shifting of a hydraulic pumpincluded in the continuously variable shift section, and alsocontrolling switching of the clutch mechanism.

In an agricultural apparatus for example, there are cases where thereare repeated switches between forward and reverse, such as the case ofchanging direction at the end of a work line. The above-described travelpower transmission apparatus has output characteristics such as thoseshown in FIG. 33, and is configured such that when operations forshifting forward and reverse via the neutral state of the continuouslyvariable shift section are performed, the output speed changes to theforward side and the reverse side along the HST shift line, and thus itis possible to switch the apparatus between forward and reverse bymerely performing a simple shift operation that does not require aspecial operation for forward/reverse switching.

In this type of travel power transmission apparatus described inaforementioned Patent Document 2, the power transmission system fortransmitting output from the engine to the front/rear wheels is providedwith a hydraulic continuously variable shift apparatus, a planetary gearmechanism, and two hydraulic clutches. An HST mode drive train isconfigured by performing connection switching with respect to the twohydraulic clutches, and in this mode, drive force output from a motoroutput shaft in the hydraulic continuously variable shift apparatus istransmitted to the front/rear wheels without being transmitted to theplanetary gear mechanism. Also, an HMT mode drive train is configured byperforming connection switching with respect to the two hydraulicclutches, and in this mode, drive force output from the motor outputshaft in the hydraulic continuously variable shift apparatus istransmitted to the planetary gear mechanism, the planetary gearmechanism combines drive force from the hydraulic continuously variableshift apparatus with drive force from the engine, and the combined driveforce output from the planetary gear mechanism is transmitted to thefront/rear wheels.

[4] There is a travel power transmission apparatus that includes a shiftpower transmission device. The shift power transmission device has ahydrostatic continuously variable shift section that operates so as toreceive drive force from an engine and subject it to speed change, thespeed-changed drive force to be output being subjected to speed changealong an HST shift line, and a planetary power transmission section thatoperates so as to receive and combine the drive force from the engineand the speed-changed drive force from the continuously variable shiftsection, the combined drive force to be output being subjected to speedchange along an HMT shift line by the speed change performed by thecontinuously variable shift section. The shift power transmission deviceis provided with a clutch mechanism that can be switched between an HSTsetting state, which is for setting HST power transmission in which thespeed-changed drive force output from the continuously variable shiftsection is outputted to a travel apparatus, and an HMT setting state,which is for setting HMT power transmission in which the combined driveforce output from the planetary power transmission section is outputtedto the travel apparatus. The travel power transmission apparatus alsoincludes a shift control module for, based on a shift instruction from ashift operation device, controlling shifting of a hydraulic pumpincluded in the continuously variable shift section, and alsocontrolling switching of the clutch mechanism.

In an agricultural apparatus for example, there are cases where thereare repeated switches between forward and reverse, such as the case ofchanging direction at the end of a work line. The above-described travelpower transmission apparatus has output characteristics such as thoseshown in FIG. 50, and is configured such that when operations forshifting forward and reverse via the neutral state of the continuouslyvariable shift section are performed, the output speed changes to theforward side and the reverse side along the HST shift line, and thus itis possible to switch the apparatus between forward and reverse bymerely performing a simple shift operation that does not require aspecial operation for forward/reverse switching.

In this type of conventional travel power transmission apparatusdescribed in aforementioned Patent Document 2, the power transmissionsystem for transmitting output from the engine to the front/rear wheelsis provided with a hydraulic continuously variable shift apparatus, aplanetary gear mechanism, and two hydraulic clutches. An HST mode drivetrain is configured by performing connection switching with respect tothe two hydraulic clutches, and in this mode, drive force output from amotor output shaft in the hydraulic continuously variable shiftapparatus is transmitted to the front/rear wheels without beingtransmitted to the planetary gear mechanism. Also, an HMT mode drivetrain is configured by performing connection switching with respect tothe two hydraulic clutches, and in this mode, drive force output fromthe motor output shaft in the hydraulic continuously variable shiftapparatus is transmitted to the planetary gear mechanism, the planetarygear mechanism combines drive force from the hydraulic continuouslyvariable shift apparatus with drive force from the engine, and thecombined drive force output from the planetary gear mechanism istransmitted to the front/rear wheels.

Also, conventionally there is a apparatus that, as shown in PatentDocument 3 for example, includes an actuator that controls the swashplate of a hydraulic motor included in a continuously variable shiftapparatus, and is configured such that the actuator operates accordingto an instruction operation performed by a switching switch, thusswitching the hydraulic motor between two stages, namely high-speed andlow-speed.

PRIOR ART DOCUMENTS Patent Documents

Patent Document 1: JP 2008-215499A

Patent Document 2: JP 2001-108061A

Patent Document 3: JP 2003-202067A

DISCLOSURE OF THE INVENTION Problem to be Solved by the Invention

[1] The following(s) is/are issue(s) corresponding to Background Art[1].

In the case of employing the conventional art described inaforementioned Cited Document 1, the distance from the site where thepump shaft receives the engine drive force to the site where it outputsdrive force to the planetary power transmission section increases due tothe hydraulic pump positioned between the two sites, thus requiring anincrease in the strength of the pump shaft in order to suppressdistortion of the pump shaft caused by the drive load of the planetarypower transmission section, and increasing the strength of the pumpshaft requires the employment of a large-size hydraulic continuouslyvariable transmission that includes a large-diameter pump shaft, forexample.

An object of the present invention is to provide a shift powertransmission apparatus for readily suppressing or avoiding size increasethereof.

[2] The following(s) is/are issue(s) corresponding to Background Art[2].

A shift power transmission apparatus is provided with an input shaftthat receives engine drive force, a hydraulic continuously variabletransmission that is driven by the input shaft, a planetary powertransmission section that combines drive force from the input shaft andoutput from the hydraulic continuously variable transmission and outputsthe combined drive force, and an output rotary member that outputs powerto a travel apparatus. When this apparatus is configured to be able toachieve HST mode power transmission, in which engine drive force that isto be transmitted to the output rotary member is subjected to speedchange by the hydraulic continuously variable transmission and is notsubjected to combining by the planetary power transmission section, andbe able to achieve HMT mode power transmission, in which engine driveforce that is to be transmitted to the output rotary member is subjectedto combining by the planetary power transmission section, it has outputcharacteristics such as those shown in FIG. 26.

FIG. 26 is an illustrative diagram showing the relationship betweenshift state of the hydraulic continuously variable transmission and theoutput speed of the output rotary member. In FIG. 26, the horizontalaxis indicates the shift state of the hydraulic continuously variabletransmission, and the vertical axis indicates the rotation direction andoutput speed of the output rotary member. Here, “n” on the horizontalaxis indicates the neutral position of the hydraulic continuouslyvariable transmission, “-max” on the horizontal axis indicates themaximum speed position in the reverse power transmission state of thehydraulic continuously variable transmission, and “+max” on thehorizontal axis indicates the maximum speed position in the forwardpower transmission state of the hydraulic continuously variabletransmission. A solid line RL shown in FIG. 26 indicates the output ofreverse drive force in the state where HST mode power transmission isachieved, a solid line FL indicates the output of forward drive force inthe state where HST mode power transmission is achieved, and a solidline FH indicates the output of forward drive force in the state whereHMT mode power transmission is achieved.

As shown by the solid line RL, in the state where HST mode powertransmission is achieved, if the hydraulic continuously variabletransmission is operated to the maximum speed position “-max” in thereverse power transmission state, the output speed reaches the reversemaximum speed “RV”. Then, while maintaining the HST mode powertransmission, as the hydraulic continuously variable transmission isshifted from the maximum speed position “−max” in the reverse powertransmission state toward the neutral position “n”, the reverse outputspeed decreases, and then the output speed reaches “0” when thehydraulic continuously variable transmission reaches the neutralposition “n”. As shown by the solid line FL, while maintaining HST modepower transmission, if the hydraulic continuously variable transmissionis shifted from the neutral position “n” to the forward powertransmission state side, the output switches from reverse output toforward output, and as the hydraulic continuously variable transmissionis shifted from the neutral position “n” toward the maximum speedposition “+max” in the forward power transmission state, the forwardoutput speed increases, and then the forward output speed reaches “FV1”when the hydraulic continuously variable transmission reaches themaximum speed position “+max” in the forward power transmission state.As shown by the solid line FH, when the hydraulic continuously variabletransmission reaches the maximum speed position “+max” in the forwardpower transmission state, HMT mode power transmission is achieved inplace of HST mode power transmission, and, while maintaining HMT modepower transmission, as the hydraulic continuously variable transmissionis shifted from the maximum speed position “+max” in the forward powertransmission state toward the maximum speed position “−max” in thereverse power transmission state, the forward output speed increases,and the forward output reaches the maximum speed “FV2” when thehydraulic continuously variable transmission reaches the maximum speedposition “−max” in the reverse power transmission state.

In other words, when HST mode power transmission and HMT mode powertransmission can be achieved, by merely performing shift operations onthe hydraulic continuously variable transmission, the output can beeasily set to zero “0” such that the travel apparatus stops, and theoutput can be easily switched between forward output and reverse outputsuch that the travel apparatus can be switched between forward andreverse driving. However, transmission efficiency is more favorable inHMT mode power transmission than in HST mode power transmission, andsince forward drive force is transmitted to the output rotary member inHMT mode power transmission, the reverse output shift range is setsmaller than the forward output shift range.

There is a configuration in which, conventional technology in which theforward/reverse switching apparatus is provided downstream of theplanetary power transmission section in the transmission direction isapplied, and output from the hydraulic continuously variabletransmission and the planetary power transmission section is inputted tothe forward/reverse switching mechanism and converted into forward driveforce and reverse drive force before being transmitted to the outputrotary member, and with this configuration, the reverse output shiftrange is similar to the forward output shift range.

On the other hand, FIG. 27 is an illustrative diagram showing therelationship between the shift state of the hydraulic continuouslyvariable transmission and the output speed of the output rotary memberin the case of a configuration in which the output of the hydrauliccontinuously variable transmission and the planetary power transmissionsection is converted into forward drive force and reverse drive force bythe forward/reverse switching mechanism before being transmitted to theoutput rotary member. Solid lines FL and FH shown in FIG. 27 indicatethe output of forward drive force, and solid lines RL and RH indicatethe output of reverse drive force.

As shown by the solid line FL, in the state where HST mode powertransmission is achieved, if the hydraulic continuously variabletransmission is operated to the neutral position “n”, the output changesto zero “0”. While maintaining HST mode power transmission, and alsoswitching the forward/reverse switching mechanism to the forward powertransmission state and maintaining the forward power transmission state,as the hydraulic continuously variable transmission changes from theneutral position “n” toward the maximum speed position “+max” in theforward power transmission state, the forward output speed increases,and then the forward output speed reaches “FV1” when the hydrauliccontinuously variable transmission reaches the maximum speed position“+max” in the forward power transmission state. As shown by the solidline FH, when the hydraulic continuously variable transmission reachesthe maximum speed position “+max” in the forward power transmissionstate, HMT mode power transmission is achieved in place of HST modepower transmission, and, while maintaining HMT mode power transmissionand also maintaining the forward/reverse switching mechanism in theforward power transmission state, as the hydraulic continuously variabletransmission is shifted from the maximum speed position “+max” in theforward power transmission state toward the maximum speed position“−max” in the reverse power transmission state, the forward output speedincreases, and then the forward output reaches the maximum speed “FV2”when the hydraulic continuously variable transmission reaches themaximum speed position “−max” in the reverse power transmission state.As shown by the solid line RL, if the hydraulic continuously variabletransmission is operated to the neutral position “n”, theforward/reverse switching mechanism is switched to the reverse powertransmission state, and, while maintaining HST mode power transmissionand also maintaining the forward/reverse switching mechanism in thereverse power transmission state, as the hydraulic continuously variabletransmission is shifted from the neutral position “n” toward the maximumspeed position “+max” in the forward power transmission state side, thereverse output speed increases, and then the reverse output speedreaches “RV1” when the hydraulic continuously variable transmissionreaches the maximum speed position “+max” in the forward powertransmission state. As shown by the solid line RH, when the hydrauliccontinuously variable transmission reaches the maximum speed position“+max” in the forward power transmission state, HMT mode powertransmission is achieved in place of HST mode power transmission, and,while maintaining HMT mode power transmission and also maintaining theforward/reverse switching mechanism in the reverse power transmissionstate, as the hydraulic continuously variable transmission is shiftedfrom the maximum speed position “+max” in the forward power transmissionstate toward the maximum speed position “−max” in the reverse powertransmission state, the reverse output speed increases, and then thereverse output reaches the maximum speed “RV2” when the hydrauliccontinuously variable transmission reaches the maximum speed position“−max” in the reverse power transmission state.

In other words, in the case of a configuration in which output from thehydraulic continuously variable transmission and the planetary powertransmission section is inputted to the forward/reverse switchingmechanism and converted into forward drive force and reverse drive forcebefore being transmitted to the output rotary member, when the travelapparatus undergoing forward driving is stopped and then switched toreverse driving, and also when the travel apparatus undergoing reversedriving is stopped and then switched to forward driving, theforward/reverse switching mechanism needs to be switched from either theforward power transmission state or the reverse power transmission stateto the other.

An object of the present invention is to provide a shift powertransmission apparatus that enables the stopping of the travel apparatusand forward/reverse switching to be performed with an easy operation,and to enable the travel apparatus to undergo reverse driving in a wideshift range, and for this to be accomplished with a simple structure.

[3] The following(s) is/are issue(s) corresponding to Background Art[3].

If the sun gear, carrier, and ring gear of the planetary powertransmission section rotate in an integrated manner at the point in timewhen switching of the clutch mechanism in order to switch the settingfrom HST power transmission setting to HMT power transmission iscompleted and drive force from the engine is transmitted to theplanetary power transmission section, the switching of the clutchmechanism in order to switch the setting from HST power transmission toHMT power transmission will be performed smoothly due to therelationship between the relative phases of the members on thetransmission upstream side and the members on the transmissiondownstream side that configure the clutch mechanism. However, there is aconfiguration in which the output speed of the continuously variableshift section is detected, and the switching of the clutch mechanism iscontrolled based on result of the detection of the output speed of thecontinuously variable shift section so as to provide an output speedthat corresponds to the output speed when in-unison rotation of the sungear, the carrier, and the ring gear of the planetary power transmissionsection is achieved (in-unison rotation achievement speed) after thesetting of the continuously variable shift section is switched when thesetting is switched from HST power transmission to HMT powertransmission. In this case, a problem tends to occur in which thetraveling speed changes immediately after the setting is switched fromHST power transmission to HMT power transmission. This will be describedwith reference to FIGS. 37 and 44.

FIG. 37 is a graph showing output characteristics of the shift powertransmission device in the travel power transmission apparatus. A speedline that indicates the rotational speed of drive force outputted by theshift power transmission device is shown on the vertical axis. Anoperation position line L that passes through the position at which therotational speed plotted on the vertical axis is zero “0”, and thatindicates the position of the swash plate of the hydraulic pumpconfiguring the continuously variable shift section is shown on thehorizontal axis. Here, “n” on the operation position line L is theoperation position corresponding to the neutral position of the swashplate at which the continuously variable shift section is put into theneutral state. Also, “a” on the operation position line L is the setforward high-speed position, which is set as the maximum speed positionon the forward side of the swash plate, which is operated in accordancewith shift control. Also, “−max” on the operation position line L is theset reverse high-speed position, which is set as the maximum speedposition on the reverse side of the swash plate, which is operated inaccordance with shift control.

A shift line S that passes through the position at which the rotationalspeed is zero “0” is a no-load HST shift line S that indicates change inthe output speed of the shift power transmission device when HST powertransmission is set and no-load driving is being performed. A shift linerange portion SF that corresponds to the range of the no-load HST shiftline S between the swash plate positions “n” and “a” is the forward-sideno-load HST shift line SF that indicates change in the output speed onthe forward side. A shift line section SR that corresponds to thesection of the no-load HST shift line S between the swash platepositions “n” and “−max” is the reverse-side no-load HST shift line SFthat indicates change in the output speed on the reverse side. A shiftline M that is continuous with the no-load HST shift line S is a no-loadHMT shift line M that indicates change in the output speed of the shiftpower transmission device when HMT power transmission is set and no-loaddriving is being performed.

A shift line SA that passes through the position at which the rotationalspeed is zero “0” is a load HST shift line SA that indicates change inthe output speed of the shift power transmission device when HST powertransmission is set and load driving is being performed. An inclinedline MA that intersects the load HST shift line SA is a load HMT shiftline MA that indicates change in the output speed of the shift powertransmission device when HMT power transmission is set and load drivingis being performed.

Since the drive load applied to the shift power transmission device actson the swash plate of the hydraulic pump configuring the continuouslyvariable shift section, the no-load HST shift line SF and HMT shift lineM are different from the load HST shift line SA and HMT shift line MA.In other words, the angle of inclination of the load HST shift line SArelative to the operation position line L is lower than the angle ofinclination of the no-load HST shift line S relative to the operationposition line L. In a simple configuration in which the rotation of theoutput shaft of the continuously variable shift section is inputtedwithout being increased/decreased by the planetary power transmissionsection, when a position in front of the actual forward maximum speedposition of an actually operable swash plate provided in the hydraulicpump of the continuously variable shift section is set as the setforward high-speed position “a” in order to maintain speed continuity atthe point where there is a switch in the setting of HST powertransmission and HMT power transmission, the angles of inclination ofthe no-load HST shift line S and HMT shift line M tend to be largelydifferent from those of the load HST shift line SA and HMT shift lineMA.

A horizontal line L1 that passes through the rotational speed “V”position on the vertical axis indicates the aforementioned in-unisonrotation achievement speed. The rotational speed “V” is the same as“V1”. FIG. 44 is an illustrative diagram showing a switch from HST powertransmission to HMT power transmission. As shown in FIGS. 37 and 44, inthe case of a configuration in which control is performed such that thesetting is switched from HST power transmission to HMT powertransmission when the output speed of the continuously variable shiftsection reaches the in-unison rotation achievement speed “V”, duringactual traveling in which the continuously variable shift section isperforming load driving, the setting is switched from HST powertransmission to HMT power transmission when the output speed of thecontinuously variable shift section, which is the output speed of theshift power transmission device, increases along the load HST shift lineSA and reaches the in-unison rotation achievement speed “V”, that is tosay, reaches the output speed that corresponds to the intersection “X”between the load HST shift line SA and the horizontal line L1. Theoutput speed of the shift power transmission device immediately afterthis switch is performed is the output speed “V0” that corresponds tothe intersection “Y” between the load HMT shift line MA and the verticalline that passes through the intersection “X”.

In other words, the output speed “V0” immediately after the setting isswitched from HST power transmission to HMT power transmission is lowerthan “V” immediately before the switch, and there is a relatively largedrop in speed. The greater the drive load is, the smaller the angle ofinclination of the load HST shift line SA relative to the operationposition line L is, and the greater the difference is between the outputspeed “V” immediately before the switch and the output speed “V0”immediately after the switch.

An object of the present invention is to provide a travel powertransmission apparatus that can suppress or eliminate a change in speedthat accompanies a switch from HST power transmission to HMT powertransmission.

[4] The following(s) is/are issue(s) corresponding to Background Art[4].

The above-described travel power transmission apparatus may beconfigured such that the hydraulic motor that configures thecontinuously variable shift section is given a variable displacementconfiguration, an auxiliary shift actuator that operates so as to changethe angle of the swash plate of the hydraulic motor is provided, and thehydraulic motor is shifted to a higher speed by controlling theauxiliary shift actuator through giving an auxiliary shift instructionby operating an auxiliary shift operation device. This is convenient dueto being able to perform high-speed traveling when, for example,location change traveling is being performed. However, there are caseswhere even if an auxiliary shift operation for shifting the hydraulicmotor to a higher speed is performed, the traveling speed decreasesinstead of increases.

Specifically, FIG. 50 is a graph showing output characteristics of ashift power transmission device. A speed line that indicates therotational speed of drive force outputted by the shift powertransmission device is shown on the vertical axis. An operation positionline L that passes through the position at which the rotational speedplotted on the vertical axis is zero “0”, and that indicates theposition of the swash plate of the hydraulic pump configuring thecontinuously variable shift section is shown on the horizontal axis.Here, “n” on the operation position line L is the operation positioncorresponding to the neutral position of the swash plate at which thecontinuously variable shift section is put into the neutral state. Also,“a” on the operation position line L is the set forward high-speedposition, which is set as the maximum speed position on the forward sideof the swash plate, which is operated in accordance with shift control.Also, “−max” on the operation position line L is the set reversehigh-speed position, which is set as the maximum speed position on thereverse side of the swash plate, which is operated in accordance withshift control.

A shift line S that passes through the position at which the rotationalspeed is zero “0” is an HST shift line S that indicates change in theoutput speed of the shift power transmission device when HST powertransmission is set. A shift line portion SF that corresponds to theportion of the HST shift line S between the swash plate positions “n”and “a” is the forward-side HST shift line SF that indicates change inthe output speed on the forward side. A shift line portion SR thatcorresponds to the portion of the HST shift line S between the swashplate positions “n” and “−max” is the reverse-side HST shift line SFthat indicates change in the output speed on the reverse side. A shiftline M that is continuous with the HST shift line S is an HMT shift lineM that indicates change in the output speed of the shift powertransmission device when HMT power transmission is set.

Control is performed such that the setting is switched between HST powertransmission and HMT power transmission when the swash plate of thehydraulic pump reaches the set forward high-speed position “a”. Theshift power transmission device in the power transmission state settingthe HMT power transmission increase the output speed, as the outputspeed of the continuously variable shift section increases due to thecontinuously variable shift section being shifted to a higher speed inthe reverse shift range. On the other hand, the shift power transmissiondevice in the power transmission state setting the HMT powertransmission increases the output speed also, as the output speed of thecontinuously variable shift section decreases due to the continuouslyvariable shift section being shifted to a lower speed in the forwardshift range.

In other words, when the shift power transmission device is set to HMTpower transmission, and furthermore is in a transmission state in whichthe combined drive force to be output is increased/decreased byperforming a shift operation on the continuously variable shift sectionin the forward shift range, if the hydraulic motor is shifted to ahigher speed, the continuously variable shift section is shifted suchthat the output speed increases, and the output speed of the shift powertransmission device decreases, and thus the traveling speed decreasesinstead of increases.

An object of the present invention is to provide a travel powertransmission apparatus that enables auxiliary shifting to be performedwith a hydraulic motor while also avoiding the above-described shiftproblem.

Means for Solving Problem

[1] The following is means for solving the problem corresponding toProblem [1]:

A shift power transmission apparatus comprising:

an input shaft receiving engine drive force;

a hydraulic continuously variable transmission driven by the inputshaft;

a planetary power transmission section combining the drive force fromthe input shaft and an output from the hydraulic continuously variabletransmission for outputting the combined drive force therefrom; and

an output rotary member outputting power to a travel apparatus,

wherein the planetary power transmission section and the output rotarymember are arranged on a side of the hydraulic continuously variabletransmission associated with an engine-coupled side of the input shaft;and

wherein the drive force is inputted to the planetary power transmissionsection from a portion between the engine-coupled side and a hydrauliccontinuously variable transmission-coupled side of the input shaft.

According to this configuration, the planetary power transmissionsection and the output rotary member are arranged on the same side ofthe hydraulic continuously variable transmission as the side on whichthe engine-coupled side of the input shaft is located, and drive forceis inputted to the planetary power transmission section from a sitebetween the engine-coupled side and the hydraulic continuously variabletransmission-coupled side of the input shaft, and thus the powertransmission structure from the input shaft to the planetary powertransmission section can be simple with as short a power transmissiondistance as possible. Since drive force is inputted to the planetarypower transmission section from a site between the engine-coupled sideand the hydraulic continuously variable transmission-coupled side of theinput shaft, the distance from the site where engine drive force isinputted to the input shaft to the site where it is outputted to theplanetary power transmission section can be made as small as possible,it is possible to suppress or avoid an increase in the size of the inputshaft in order to suppress distortion of the input shaft caused by thedrive load of the planetary power transmission section, it is possibleto suppress drive load from being applied from the planetary powertransmission section to the pump shaft, and it is possible to suppressor avoid an increase in the size of the pump shaft and suppress or avoidan increase in the size of the hydraulic continuously variabletransmission.

Accordingly, in terms of the power transmission structure for powertransmission from the input shaft to the planetary power transmissionsection, and in terms of the input shaft and the hydraulic continuouslyvariable transmission, it is possible to obtain compactness in which anincrease in size is suppressed or avoided.

In a preferred embodiment, the input shaft is coupled to a pump shaft ofthe hydraulic continuously variable transmission be rotatable in unisonwith each other, the input shaft being coaxially aligned with the pumpshaft, and

wherein a sun gear of the planetary power transmission section and theoutput rotary member are supported to be rotatable about a rotation axisextending coaxial with a motor shaft of the hydraulic continuouslyvariable transmission.

According to this configuration, the driving of the hydrauliccontinuously variable transmission by the input shaft can be achievedwith a compact interlocking structure in which the input shaft and thepump shaft are arranged coaxially. Furthermore, power transmission fromthe hydraulic continuously variable transmission to the planetary powertransmission section and power transmission from the planetary powertransmission section to the output rotary member can be achieved with acompact interlocking structure in which the sun gear, the output rotarymember, and the motor shaft are arranged coaxially.

Accordingly, in terms of the driving of the hydraulic continuouslyvariable transmission by the input shaft, and in terms of powertransmission from the hydraulic continuously variable transmission tothe planetary power transmission section and power transmission from theplanetary power transmission section to the output rotary member,compactness can be achieved.

In a preferred embodiment, the shift power transmission apparatusfurther comprises:

an input-side clutch mechanism switching the planetary powertransmission section between an interlocking-on state and aninterlocking-off state with respect to the input shaft; and

an output-side clutch mechanism switching the output rotary memberbetween an interlocking-on state and an interlocking-off state withrespect to the motor shaft of the hydraulic continuously variabletransmission.

According to this configuration, when the planetary power transmissionsection is switched to the interlocking-off state with respect to theinput shaft, and the output rotary member is switched to theinterlocking-on state with respect to the motor shaft, shifting by HSTmode power transmission can be performed such that engine drive forceinput by the input shaft is outputted from the output rotary memberafter being subjected to speed change by the hydraulic continuouslyvariable transmission. When the planetary power transmission section isswitched to the interlocking-on state with respect to the input shaft,and the output rotary member is switched to the interlocking-off statewith respect to the motor shaft, shifting by HMT mode power transmissioncan be performed such that engine drive force input by the input shaftis transmitted to the planetary power transmission section, the enginedrive force and output from the hydraulic continuously variabletransmission are combined by the planetary power transmission section,and the combined drive force is outputted from the output rotary member.

Accordingly, it is possible to perform outputted by HST mode powertransmission, and perform travel stop and forward/reverse switching witha simple operation performed by performing a shift operation on thehydraulic continuously variable transmission, and it is possible toperform outputted by HMT mode power transmission and perform travel atvarious speeds with favorable power transmission efficiency.

In a preferred embodiment, the shift power transmission apparatusfurther comprises:

a charge pump supplying hydraulic oil to the hydraulic continuouslyvariable transmission, the charge pump being provided between theengine-coupled side and the hydraulic continuously variabletransmission-coupled side of the input shaft.

According to this configuration, drive load of the charge pump isapplied between the engine-coupled side and the hydraulic continuouslyvariable transmission-coupled side of the input shaft, and is notreadily applied to the pump shaft of the hydraulic continuously variabletransmission.

Accordingly, the charge pump is driven by drive force from the inputshaft, and it is possible to suppress an increase in the size of thepump shaft of the hydraulic continuously variable transmission, and toadvantageously achieve the hydraulic continuously variable transmission.

In a preferred embodiment, the shift power transmission apparatusfurther comprises:

a charge pump supplying hydraulic oil to the hydraulic continuouslyvariable transmission, the charge pump being provided between theengine-coupled side of the input shaft and an input-side clutchmechanism.

The hydraulic continuously variable transmission does not exist betweenthe engine-coupled side of the input shaft and the input-side clutchmechanism, and it is easy to ensure pump arrangement space, andaccording to this configuration, the charge pump can be compactlyprovided at a site where it is easy to ensure pump arrangement space.

Accordingly, the charge pump is driven by drive force from the inputshaft, and it is possible to achieve a simple apparatus in which thecharge pump is provided in a compact manner.

[2] The following is means for solving the problem corresponding toProblem [2]:

A shift power transmission apparatus comprising:

an input shaft receiving engine drive force;

a hydraulic continuously variable transmission driven by the inputshaft;

a planetary power transmission section combining the drive force fromthe input shaft and an output from the hydraulic continuously variabletransmission for outputting the combined drive force therefrom; and

an output rotary member outputting power to a travel apparatus,

wherein a forward/reverse switching mechanism is provided to beswitchable between a forward power transmission state for converting thedrive force from the input shaft into forward drive force to betransmitted to the planetary power transmission section, and a reversepower transmission state for converting the drive force from the inputshaft into reverse drive force to be transmitted to the planetary powertransmission section, and

the forward/reverse switching mechanism is further switchable to aneutral state in which power transmission between the input shaft andthe planetary power transmission section is cut off; and

wherein a clutch mechanism is provided for switching interlock from themotor shaft of the hydraulic continuously variable transmission to theoutput rotary member between an on state and an off state.

According to this configuration, when the forward/reverse switchingmechanism is switched to the neutral state, and the clutch mechanism isswitched so that the motor shaft of the hydraulic continuously variabletransmission and the output rotary member are put into theinterlocking-on state, it is possible to achieve HST mode powertransmission in which the hydraulic continuously variable transmissionis driven by engine drive force input by the input shaft, the enginedrive force input by the input shaft is not transmitted to the planetarypower transmission section, the engine drive force is subjected to speedchange by the hydraulic continuously variable transmission, and thentransmitted to the output rotary member.

When the forward/reverse switching mechanism is switched to the forwardpower transmission state, and the clutch mechanism is switched so thatthe motor shaft of the hydraulic continuously variable transmission andthe output rotary member are put into the interlocking-off state, it ispossible to achieve forward-side HMT mode power transmission in whichthe hydraulic continuously variable transmission is driven by enginedrive force input by the input shaft, the engine drive force input bythe input shaft is converted into forward drive force by theforward/reverse switching mechanism and transmitted to the planetarypower transmission section, output from the hydraulic continuouslyvariable transmission and forward drive force from the forward/reverseswitching mechanism are combined by the planetary power transmissionsection, the planetary power transmission section outputs theforward-side combined drive force, and the forward-side combined driveforce is transmitted to the output rotary member.

When the forward/reverse switching mechanism is switched to the reversepower transmission state, and the clutch mechanism is switched so thatthe motor shaft of the hydraulic continuously variable transmission andthe output rotary member are put into the interlocking-off state, it ispossible to achieve reverse-side

HMT mode power transmission in which the hydraulic continuously variabletransmission is driven by engine drive force input by the input shaft,the engine drive force input by the input shaft is converted intoreverse drive force by the forward/reverse switching mechanism andtransmitted to the planetary power transmission section, output from thehydraulic continuously variable transmission and reverse drive forcefrom the forward/reverse switching mechanism are combined by theplanetary power transmission section, the planetary power transmissionsection outputs the reverse-side combined drive force, and thereverse-side combined drive force is transmitted to the output rotarymember.

In other words, when the forward/reverse switching mechanism and theclutch mechanism are appropriately operated in accordance with a shiftoperation performed on the hydraulic continuously variable transmission,the relationship between the shift state of the hydraulic continuouslyvariable transmission and the output speed of the output rotary memberis as shown in FIG. 23. Specifically, as shown by a solid line FL inFIG. 23, in the state where HST mode power transmission is achieved, ifthe hydraulic continuously variable transmission is operated to theneutral position “n”, the output changes to zero “0”. While maintainingHST mode power transmission, as the hydraulic continuously variabletransmission is shifted from the neutral position “n” toward the maximumspeed position “+max” in the forward power transmission state, theforward output speed increases, and then the forward output speedreaches “FV1” when the hydraulic continuously variable transmissionreaches the maximum speed position “+max” in the forward powertransmission state. As shown by solid lines FM and FH, when thehydraulic continuously variable transmission reaches the maximum speedposition “+max” in the forward power transmission state, HMT mode powertransmission is achieved in place of HST mode power transmission, and,while maintaining forward-side HMT mode power transmission, as thehydraulic continuously variable transmission is shifted from the maximumspeed position “+max” in the forward power transmission state toward themaximum speed position “−max” in the reverse power transmission state,the forward output speed increases steplessly, and the forward outputreaches the maximum speed “FV2” when the hydraulic continuously variabletransmission reaches the maximum speed position “−max” in the reversepower transmission state.

As shown by the solid line RL, in the state in which HST mode powertransmission is maintained, if the hydraulic continuously variabletransmission is shifted from the neutral position “n” toward the maximumspeed position “−max” in the reverse power transmission state, theoutput changes to reverse output, and as the hydraulic continuouslyvariable transmission is shifted from the neutral position “n” towardthe maximum speed position “−max” in the reverse power transmissionstate, the reverse output speed increases steplessly, and then thereverse output speed reaches “RV1” when the hydraulic continuouslyvariable transmission reaches the maximum speed position “−max” in thereverse power transmission state. As shown by solid lines RM and RH,when the hydraulic continuously variable transmission reaches themaximum speed position “−max” in the reverse power transmission state,reverse-side HMT mode power transmission is achieved in place of HSTmode power transmission, and, while maintaining reverse-side HMT modepower transmission, as the hydraulic continuously variable transmissionis shifted from the maximum speed position “−max” in the reverse powertransmission state to the maximum speed position “+max” in the forwardpower transmission state, the reverse output speed increases steplessly,and the reverse output reaches the maximum speed “RV2” when thehydraulic continuously variable transmission reaches the maximum speedposition “+max” in the forward power transmission state. The maximumreverse output speed “RV2” is higher than the reverse output speed “RV1”when the hydraulic continuously variable transmission is operated to themaximum speed position “−max” in the reverse power transmission state.

By merely performing a shift operation on the hydraulic continuouslyvariable transmission in the shift range from the forward output speed“FV1” to the reverse output speed “RV1”, it is possible to performshifting and forward/reverse switching without switching theforward/reverse switching mechanism.

Accordingly, it is possible to stop the travel apparatus with a simpleoperation by merely shifting the hydraulic continuously variabletransmission to the neutral position, it is possible to switch thetravel apparatus between forward driving and reverse driving with asimple operation by merely shifting the hydraulic continuously variabletransmission from the neutral position to a forward position or areverse position, and in the case of driving the travel apparatus inreverse, it is possible to perform driving at various speeds over a wideshift range in reverse-side HMT mode power transmission, and in acombine, dozer vehicle, or the like, forward and reverse can be easilyrepeated, relatively high-speed reverse travel is possible, andadjustment and position changing and the like can be performing easily,swiftly, and efficiently.

Furthermore, HST mode power transmission can be achieved by cutting offpower transmission to the planetary power transmission section withusing the forward/reverse switching mechanism as a clutch device, andthis can be achieved with a simple structure.

In a preferred embodiment, in the on state of the clutch mechanism, asun gear, a planet gear and a ring gear of the planetary powertransmission section are interlocked with the motor shaft of thehydraulic continuously variable transmission to be rotatable with themotor shaft.

According to this configuration, when HST mode power transmission isachieved, the sun gear, planet gears, and ring gear of the planetarypower transmission section rotate in unison with the motor shaft, andthere is no relative rotation of the sun gear and the planet gears, andno relative rotation of the planet gears and the ring gear.

This enables performing power transmission by HST mode powertransmission while avoiding power loss caused by relative rotation ofthe sun gear, the planet gears, and the ring gear.

In a preferred embodiment, the forward/reverse switching mechanismincludes:

a forward power transmission gear supported on the input shaft to berotatable relative thereto, the forward power transmission gear beinginterlocked with the planetary power transmission section;

a forward clutch member supported on the input shaft to be rotatable inunison therewith and slidable relative thereto for switching the forwardpower transmission gear and the input shaft between an interlocking-onstate and an interlocking-off state in association with engagement withand disengagement from the forward power transmission gear;

a reverse power transmission shaft supporting one of the input gearinterlocked with the input shaft and the reverse power transmission gearinterlocked with the planetary power transmission section to berotatable relative thereto, and the reverse power transmission shaftsupporting thereon the other of the input gear and the reverse powertransmission gear to rotatable in unison therewith; and

a reverse clutch member supported on the reverse power transmissionshaft to be rotatable in unison therewith and slidable relative thereto,wherein when the reverse clutch member is engaged with and disengagedfrom the one of the input gear and the reverse power transmission gear,which one gear is supported on the reverse power transmission shaft tobe rotatable relative thereto to be clutched by the reverse clutchmember, the reverse clutch member switches the one gear and the reversepower transmission shaft between an interlocking-on state and aninterlocking-off state.

According to this configuration, the forward clutch member can besupported using the input shaft as the support shaft, and thisconsequently makes it possible for simply the reverse power transmissionshaft to be used as the power transmission shaft that is to be added,and for the forward/reverse switching mechanism to be configured with asimple structure.

This makes it possible for the forward/reverse switching mechanism to beconfigured inexpensively and with a simple structure.

In a preferred embodiment, the input gear, and a power transmission gearsupported on the input shaft to be rotatable in unison and meshtherewith, are arranged on a side of the planetary power transmissionsection opposite from the forward power transmission gear and thereverse power transmission gear, and

wherein the forward power transmission gear and the reverse powertransmission gear are meshed with a second input gear provided at aportion of the sun gear of the planetary power transmission sectionopposite from the input gear and the power transmission gear.

According to this configuration, the outer peripheral side portion ofthe planetary power transmission section is arranged in between theinput gear and the reverse power transmission gear or in between thepower transmission gear and the forward power transmission gear, thusmaking it possible for the forward/reverse switching mechanism and theplanetary power transmission section to be disposed together compactly.

This makes it possible to obtain a small-sized shift power transmissionapparatus in which the forward/reverse switching mechanism and theplanetary power transmission section are arranged together compactly.

[3] The following is means for solving the problem corresponding toProblem [3]:

A travel power transmission apparatus comprising:

a shift power transmission device including a hydrostatic continuouslyvariable shift section and a planetary power transmission section; thehydrostatic continuously variable shift section receiving drive forcefrom an engine and outputting the drive force after changing speed ofthe drive force along an HST shift line by the continuously variableshift section; and the planetary power transmission section receivingand combining the drive force from the engine and the speed-changeddrive force from the continuously variable shift section, and outputtingthe combined drive force after changing speed of the combined driveforce along an HMT shift line by the continuously variable shiftsection;

the shift power transmission device further including a clutch mechanismswitchable between an HST setting state in which HST power transmissionis set for outputting the speed-changed drive force from thecontinuously variable shift section to a travel apparatus, and an HMTsetting state in which HMT power transmission is set for outputting thecombined drive force from the planetary power transmission section isoutputted to the travel apparatus; and

a shift control module for performing shift control on a hydraulic pumpof the continuously variable shift section and switch control on theclutch mechanism, based on a shift instruction from a shift operationdevice,

wherein the travel power transmission apparatus further comprises:

-   -   a swash plate angle sensor detecting a swash plate angle of the        hydraulic pump; and    -   a shift swash plate angle setting module for setting, as a set        shift swash plate angle of the hydraulic pump, the swash plate        angle between a no-load swash plate angle and a load swash plate        angle, wherein the no-load swash plate angle is achieved by the        hydraulic pump in a shift state for outputting speed-changed        drive force at a speed corresponding to an in-unison rotation        achievement speed at which the continuously variable shift        section achieves in-unison rotation of a sun gear, a carrier and        a ring gear of the planetary power transmission section during        the HST power transmission and no-load driving, and wherein the        load swash plate angle is achieved by the hydraulic pump in a        shift state for outputting the speed-changed drive force at a        speed corresponding to the in-unison rotation achievement speed        of the continuously variable shift section during the HST power        transmission and set load driving; and

wherein the shift control module is configured to control the clutchmechanism to be switched from the HST setting state to the HMT settingstate when the swash plate angle sensor detects the swash plate angleequal to the set shift swash plate angle.

According to this configuration, the setting is switched from HST powertransmission to HMT power transmission as shown in FIG. 39.

Specifically, when the setting is switched from HST power transmissionto HMT power transmission not at the point in time when the output speedof the continuously variable shift section increasing along the load HSTshift line SA reaches the in-unison rotation achievement speed “V”, butrather at the point in time when it reaches the output speed “VS” thatcorresponds to the intersection “S1” between the load HST shift line SAand the vertical line that passes through the set shift swash plateangle “c”, and the output speed achieved by the shift power transmissiondevice immediately after the setting is switched from HST powertransmission to HMT power transmission is the output speed “VM” thatcorresponds to the intersection “M1” between the load HMT shift line MAand the vertical line that passes through the set shift swash plateangle “c”.

Specifically, the output speed “VS” of the continuously variable shiftsection when the setting is switched from HST power transmission to HMTpower transmission is an output speed that is slower than the in-unisonrotation achievement speed “V”. Furthermore, the output speed “VM”immediately after the setting is switched from HST power transmission toHMT power transmission is faster than the output speed “V0” of the shiftpower transmission device immediately after the switch when the settingis switched from HST power transmission to HMT power transmission whenthe output speed of the continuously variable shift section reaches thein-unison rotation achievement speed “V”. Also, the amount of change inthe traveling speed that accompanies a switch from HST powertransmission to HMT power transmission can correspond to the differencein speed between the output speed “VS” immediately before the switch andthe output speed “VM” immediately after the switch, and this differencein speed can be made smaller than the difference in speed between theoutput speed “V” immediately before the switch and the output speed “V0”immediately after the switch when the switching of the setting from HSTpower transmission to HMT power transmission is performed based on theoutput speed.

According to the setting of the set shift swash plate angle “c”, thesetting is switched from HST power transmission to HMT powertransmission as shown in FIG. 41.

Specifically, when the setting is switched from HST power transmissionto HMT power transmission when the output speed of the continuouslyvariable shift section increasing along the load HST shift line SAreaches the output speed VS1 that corresponds to the intersection “W”between the load HST shift line SA and the load HMT shift line MA, andthe output speed “VS1” of the continuously variable shift sectionimmediately before the setting is switched and the output speed “VM1” ofthe shift power transmission device immediately after the setting isswitched are the output speed that corresponds to the intersection “W”.

Specifically, the output speed “VS1” of the continuously variable shiftsection immediately before the setting is switched from HST powertransmission to HMT power transmission is the same as the output speed“VM1” of the shift power transmission device immediately after thesetting is switched from HST power transmission to HMT powertransmission, and it is possible to eliminate change in the travelingspeed that accompanies a switch in the setting from HST powertransmission to HMT power transmission.

Accordingly, the setting can be switched from HST power transmission toHMT power transmission, forward/reverse switching can be performed witha simple operation by merely shifting forward or reverse via the neutralposition of the continuously variable shift section, and it is possibleto shift from an HST power transmission speed range to an HMT powertransmission speed range comfortably and with little shift shock andunpleasantness caused by a reduction in speed.

In a preferred embodiment, the shift swash plate angle setting modulehas an adjustable configuration such that the setting of the set shiftswash plate angle can be changed.

According to this configuration, the set shift swash plate angle ischanged by the adjustment of the shift swash plate angle setting module,and it is possible to suppress or prevent a large change in travelingspeed due to a change in drive load when the swash plate angle forswitching the setting from HST power transmission to HMT powertransmission is changed and then the setting is switched from HST powertransmission to HMT power transmission.

Accordingly, even if the drive load changes due to being in a differentwork field or the like, shifting from an HST power transmission speedrange to an HMT power transmission speed range can be performedcomfortably with little or no shift shock or unpleasantness.

In a preferred embodiment, the shift swash plate angle setting module isconfigured to:

calculate and set a calculated HST shift line for the HST powertransmission and the load driving based on detection information fromthe swash plate angle sensor,

calculate and set a calculated HMT shift line corresponding to thecalculated HST shift line,

determine the swash plate angle achieved by the hydraulic pump in ashift state in which the continuously variable shift section outputs thespeed-changed drive force at a speed corresponding to an intersectionbetween the calculated HST shift line and the calculated HMT shift line,and

set the determined swash plate angle as the set shift swash plate angle.

According to this configuration, even if the drive load changes duringtraveling and a load HST shift line with a different angle ofinclination appears, a calculated HST shift line and a calculated HMTshift line that correspond to the changing drive load are calculated andset. Based on the calculated HST shift line and the calculated HMT shiftline, the swash plate angle that corresponds to the intersection betweenthe calculated HST shift line and the calculated HMT shift line and isthe swash plate angle at which the traveling speed immediately beforethe switch from the HST power transmission to the HMT power transmissionis the same as the traveling speed immediately after the switch isdetermined and set as the set shift swash plate angle, and then theswitch from HST power transmission to HMT power transmission isperformed. This enables making a change in traveling speed thataccompanies a switch from HST power transmission to HMT powertransmission slight or non-existent.

Accordingly, even if the drive load changes during traveling, shiftingfrom an HST power transmission speed range to an HMT power transmissionspeed range can be performed comfortably with little or no shift shockor unpleasantness.

[4] The following is means for solving the problem corresponding toProblem [4]:

A travel power transmission apparatus comprising:

a shift power transmission device including a hydrostatic continuouslyvariable shift section and a planetary power transmission section; thehydrostatic continuously variable shift section receiving drive forcefrom an engine and outputting the drive force after changing speed ofthe drive force along an HST shift line by the continuously variableshift section; and the planetary power transmission section receivingand combining the drive force from the engine and the speed-changeddrive force from the continuously variable shift section, and outputtingthe combined drive force after changing speed of the combined driveforce along an HMT shift line by the continuously variable shiftsection;

the shift power transmission device further including a clutch mechanismswitchable between an HST setting state in which HST power transmissionis set for outputting the speed-changed drive force from thecontinuously variable shift section to a travel apparatus, and an HMTsetting state in which HMT power transmission is set for outputting thecombined drive force from the planetary power transmission section isoutputted to the travel apparatus; and

a shift control module for performing shift control on a hydraulic pumpof the continuously variable shift section and switch control on theclutch mechanism, based on a main shift instruction from a main shiftoperation device,

wherein a hydraulic motor of the continuously variable shift section isprovided in form of a variable displacement motor,

the travel power transmission apparatus further comprises an auxiliaryshift operation device which is manually operable to issue an auxiliaryshift instruction, and an auxiliary shift actuator operable to change aswash plate angle of the hydraulic motor,

the shift control module is configured to control the auxiliary shiftactuator such that the hydraulic motor is shifted to a higher speed sidebased on the auxiliary shift instruction, and

wherein the travel power transmission apparatus further comprises arestraint control module, the restraint control module being configuredsuch that:

when the shift power transmission device is set to the HMT powertransmission, and when a power transmission state is achieved in whichthe combined drive force to be outputted to the travel apparatus isincreased in response to a speed-increase shift operation in a reverseshift range of the continuously variable shift section, and in which thecombined drive force to be outputted to the travel apparatus isdecreased in response to a speed-decrease shift operation in the reverseshift range of the continuously variable shift section, the restraintcontrol module cancels restraint to permit control on the auxiliaryshift actuator by the shift control module; and

when the shift power transmission device is set to the HMT powertransmission, and when a power transmission state is achieved in whichthe combined drive force to be outputted to the travel apparatus isincreased in response to a speed-decrease shift operation in the forwardshift range of the continuously variable shift section, and in which thecombined drive force to be outputted to the travel apparatus isdecreased in response to a speed-increase shift operation in the forwardshift range of the continuously variable shift section, the restraintcontrol module performs restraint to stop control on the auxiliary shiftactuator by the shift control module.

According to this configuration, when the shift power transmissiondevice is set to HMT power transmission and is in the power transmissionstate in which the combined drive force to be outputted to the travelapparatus is increased by shifting the continuously variable shiftsection to a higher speed in the reverse shift range, the restraintcontrol module cancels restraint with respect to the shift controlmodule, and when an auxiliary shift instruction is issued due to theauxiliary shift operation device being operated, the shift controlmodule controls the auxiliary shift actuator so as to shift thehydraulic motor to a higher speed. Since the hydraulic motor is shiftedto a higher speed in the power transmission state in which the outputspeed of the shift power transmission device increases by increasing theoutput speed of the continuously variable shift section, the outputspeed of the shift power transmission device increases in response to anincrease in the speed of the hydraulic motor.

According to this configuration, when the shift power transmissiondevice is set to HMT power transmission and is in the power transmissionstate in which the combined drive force to be outputted to the travelapparatus is increased by shifting the continuously variable shiftsection to a lower speed in the forward shift range, the restraintcontrol module performs restraint on the shift control module, and evenif an auxiliary shift instruction is issued due to the auxiliary shiftoperation device being operated, the hydraulic motor is not shifted to ahigher speed by the shift control module. This enables avoiding theoccurrence of a situation in which the output speed of the shift powertransmission device decreases when the hydraulic motor is shifted to ahigher speed regardless of being in the power transmission state inwhich the output speed of the shift power transmission device increasesdue to a decrease in the output speed of the continuously variable shiftsection.

Accordingly, the setting can be switched between HST power transmissionand HMT power transmission, the device can be switched between forwardand reverse with a simple operation of merely performing a forward orreverse shift operation via the neutral state of the continuouslyvariable shift section, auxiliary shifting can be performed by shiftingof the hydraulic motor, and shifting can be performed comfortablywithout the problem where the traveling speed decreases regardless ofthe fact that the auxiliary shift operation device was operated.

In a preferred embodiment, the travel power transmission apparatusfurther comprises:

a reference swash plate angle setting module configured to set, as areference swash plate angle, a swash plate angle of the hydraulic pumplocated on a lower speed side by a set angle relative to the swash plateangle at which the HST power transmission is switched to the HMT powertransmission,

wherein when the shift power transmission device is set to the HST powertransmission, and when the swash plate angle of the hydraulic pump is onthe low speed side relative to the reference swash plate angle, therestraint control module cancels the restraint, and

wherein when the shift power transmission device is set to the HST powertransmission, and when the swash plate angle of the hydraulic pump is onthe high speed side relative to the reference swash plate angle, therestraint control module performs the restraint.

When HST power transmission is set and auxiliary shifting for shiftingthe hydraulic motor to a higher speed is performed, and when the outputspeed increases along the auxiliary shifting setting HST shift line,which is shifted from the HST shift line where there is no auxiliaryshifting setting, an intersection between the HMT shift line and the HSTshift line for when auxiliary shifting is not set for switching thesetting from HST power transmission to HMT power transmission ceases toappear, and it becomes difficult to smoothly switch the clutch mechanismfor switching the setting from HST power transmission to HMT powertransmission. In contrast, according to the above configuration, whenthe swash plate angle of the hydraulic pump exceeds the reference swashplate angle, the restraint control module enters the state of performingrestraint on the shift control module, and it is not possible to setauxiliary shifting by shifting the hydraulic motor to a higher speed.This makes it possible to reliably cause the intersection between theHMT shift line and the HST shift line for when auxiliary shifting is notset to appear, and to smoothly switch the clutch mechanism for switchingthe setting from HST power transmission to HMT power transmission.

Accordingly, it is possible to perform auxiliary shifting by shiftingthe hydraulic motor, and a shift from an HST power transmission speedrange to an HMT power transmission speed range can be performedcomfortably and without shift shock by smoothly switching the clutchmechanism.

In a preferred embodiment, when the restraint control module performsthe restraint, the shift control module is configured to perform shiftcontrol on the hydraulic pump based on the main shift instruction andthe auxiliary shift instruction such that the output speed of the shiftpower transmission device corresponding to the main shift instructionwill increase in accordance with the auxiliary shift instruction.

If the restraint control module performs restraint so that auxiliaryshifting by the hydraulic motor is not performed even if the auxiliaryshift operation device is operated, and the traveling speed does notincrease, unpleasantness will be felt, in that the traveling speed willnot increase even though an auxiliary shifting operation is beingperformed. According to this configuration, if the restraint controlmodule is performing restraint so that auxiliary shifting by thehydraulic motor is not performed even if the auxiliary shift operationdevice is operated, the shift control module performs shift control onthe hydraulic pump, and the output speed of the shift power transmissiondevice increases in accordance with the main shift instruction, and thetravel speed can be increased.

Accordingly, when the auxiliary shift operation device is operated, evenif auxiliary shifting by the hydraulic motor is not performed, auxiliaryshifting is performed by the hydraulic pump, thus enabling performingfavorable shifting without unpleasantness in that the travel speed doesnot increase even though an auxiliary shift operation is performed.

Other features and advantageous effects achieved by them will becomeapparent from reading the following description with reference to theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a figure pertaining to a first embodiment (the same followsthrough to FIG. 16), showing a side view of an entire combine.

FIG. 2 is a schematic front view of a power transmission structure.

FIG. 3 is a front view in vertical section showing a shift powertransmission apparatus during HMT (Hydraulic Mechanical Transmission)mode power transmission.

FIG. 4 is a front view in vertical section showing the shift powertransmission apparatus during HST (Hydraulic Static Transmission) modepower transmission.

FIG. 5 is an illustrative diagram showing the relationship that theoperation states of an input-side clutch mechanism and an output-sideclutch mechanism, the operation state of a power transmission switchingclutch mechanism and the power transmission mode of the shift powertransmission apparatus have with each other.

FIG. 6 is an illustrative diagram showing the relationship between theshift state of a hydraulic continuously variable transmission and theoutput speed of the shift power transmission apparatus.

FIG. 7 is a block diagram showing a shift operation apparatus.

FIG. 8 is a front view in vertical section of a shift power transmissionapparatus having a first alternative embodiment structure.

FIG. 9 is an illustrative diagram showing the relationship that theoperation states of a hydraulic continuously variable transmission, aforward clutch, a reverse clutch and an output-side clutch mechanismhave with the power transmission mode of the shift power transmissionapparatus.

FIG. 10 is an illustrative diagram showing the output speed of the shiftpower transmission apparatus having the first alternative embodimentstructure.

FIG. 11 is a block diagram showing the shift operation apparatus thatperforms shift operations on the shift power transmission apparatushaving the first alternative embodiment structure.

FIG. 12 is a front view in vertical section of a shift powertransmission apparatus having a second alternative embodiment structure.

FIG. 13 is a front view in vertical section of a shift powertransmission apparatus having a third alternative embodiment structure.

FIG. 14 is a front view in vertical section of a shift powertransmission apparatus having a fourth alternative embodiment structure.

FIG. 15 is a front view in vertical section of a shift powertransmission apparatus having a fifth alternative embodiment structure.

FIG. 16 is a front view in vertical section of a shift powertransmission apparatus having a sixth alternative embodiment structure.

FIG. 17 is a figure pertaining to a second embodiment (the same followsthrough to FIG. 27), showing a side view of an entire combine.

FIG. 18 is a schematic front view of a power transmission structure.

FIG. 19 is a front view in vertical section of a shift powertransmission apparatus during HST mode power transmission.

FIG. 20 is a front view in vertical section of the shift powertransmission apparatus during forward-side HMT mode power transmission.

FIG. 21 is a front view in vertical section of the shift powertransmission apparatus during reverse-side HMT mode power transmission.

FIG. 22 is an illustrative diagram showing the relationship that theoperation states of a hydraulic continuously variable transmission, aforward clutch, a reverse clutch and an output-side clutch mechanismhave with the power transmission mode of the shift power transmissionapparatus.

FIG. 23 is an illustrative diagram showing the relationship betweenshift state of a hydraulic continuously variable transmission and theoutput speed of the shift power transmission apparatus.

FIG. 24 is a block diagram showing a shift operation apparatus.

FIG. 25 is a front view in vertical section of a shift powertransmission apparatus having an alternative embodiment structure.

FIG. 26 is an illustrative diagram showing output characteristics of ashift power transmission apparatus having a comparative structure.

FIG. 27 is an illustrative diagram showing output characteristics of ashift power transmission apparatus having a comparative structure.

FIG. 28 is a figure pertaining to a third embodiment (the same followsthrough to FIG. 44), showing a side view of an entire combine.

FIG. 29 is a schematic front view of a travel power transmissionapparatus.

FIG. 30 is a front view in vertical section of a shift powertransmission device during HMT power transmission.

FIG. 31 is a front view in vertical section of the shift powertransmission device during HST power transmission.

FIG. 32 is an illustrative diagram showing the relationship that theoperation states of an HMT clutch and an HST clutch, the operation stateof a power transmission switching clutch mechanism, and the powertransmission mode of the shift power transmission device have with eachother.

FIG. 33 is a graph showing output characteristics of the shift powertransmission device during no-load driving.

FIG. 34 is an illustrative diagram showing the relationship between thevalue of N/X and overall efficiency.

FIG. 35 is an illustrative diagram showing the relationship between thevalue of N/X and size reduction of a continuously variable shiftsection.

FIG. 36 is a block diagram showing a shift operation apparatus.

FIG. 37 is a graph showing output characteristics of a shift powertransmission device.

FIG. 38 is a flowchart of setting switching control.

FIG. 39 is an illustrative diagram showing switching of the setting fromHST power transmission to HMT power transmission.

FIG. 40 is a block diagram showing a shift operation apparatus accordingto a first alternative embodiment.

FIG. 41 is an illustrative diagram showing a switch from HST powertransmission to HMT power transmission in the shift operation apparatusaccording to the first alternative embodiment.

FIG. 42 is a block diagram showing a shift operation apparatus accordingto a second alternative embodiment.

FIG. 43 is an illustrative diagram showing control for switching thesetting from HST power transmission to HMT power transmission in theshift operation apparatus according to the second alternativeembodiment.

FIG. 44 is an illustrative diagram showing switching of the setting fromHST power transmission to HMT power transmission in a comparativeexample.

FIG. 45 is a figure pertaining to a fourth embodiment (the same followsthrough to FIG. 54), showing a side view of an entire combine.

FIG. 46 is a schematic front view of a travel power transmissionapparatus.

FIG. 47 is a front view in vertical section of a shift powertransmission device during HMT power transmission.

FIG. 48 is a front view in vertical section of the shift powertransmission device during HST power transmission.

FIG. 49 is an illustrative diagram showing the relationship that theoperation states of an HMT clutch and an HST clutch, the operation stateof a power transmission switching clutch mechanism and the powertransmission mode of the shift power transmission apparatus have witheach other.

FIG. 50 is a graph showing output characteristics of the shift powertransmission device.

FIG. 51 is an illustrative diagram showing the relationship between N/Xvalues and overall efficiency.

FIG. 52 is an illustrative diagram showing the relationship between N/Xvalues and size reduction of a continuously variable shift section.

FIG. 53 is a block diagram showing a shift operation apparatus.

FIG. 54 is a plan view of operation positions of a main shift operationdevice.

Embodiments of the Invention

Embodiments of the present invention applied to a combine will bedescribed hereinafter with reference to the drawings.

First Embodiment

As shown in FIG. 1, the combine, which performs the task of harvestingrice, barley, and the like, is configured to be self-propelled with apair of right and left crawling travel apparatuses 1, and is configuredto include a traveling body equipped with a riding driving section 2, areaping section 4 coupled to the front portion of a body frame 3 of thetraveling body, a threshing apparatus 5 provided so as to be arrangedrearward of the reaping section 4 on the rear side of the body frame 3,and a grain tank 6 provided so as to be arranged to the side of thethreshing apparatus 5 on the rear side of the body frame 3.

Specifically, the reaping section 4 includes a reaping section frame 4 athat extends forward from the front portion of the body frame 3 in avertically swingable manner, and when the reaping section frame 4 a isswung by an elevating cylinder 7, the reaping section 4 moves up/downbetween a lowered operating position at which a divider 4 b, which isprovided at the front edge portion of the reaping section 4, is loweredclose to the ground, and a raised non-operating position at which thedivider 4 b is raised high above the ground. When the traveling body iscaused to travel with the reaping section 4 lowered to the loweredoperating position, the reaping section 4 operates such thatreaping-target planted stalks are guided to a raising path by thedivider 4 b, the planted stalks that were guided to the raising path arereaped by a clipper-type reaping apparatus 4 d while being raised up bya raising apparatus 4 c, and the reaped stalks are supplied to thethreshing apparatus 5 by a supplying apparatus 4 e. In the threshingapparatus 5, the reaped stalks are conveyed from the supplying apparatus4 e toward the rear of the apparatus body with their base sides clampedby a threshing feed chain 5 a, the ear tip-sides of the reaped stalksare supplied to a handling compartment (not shown) where they aresubjected to reaping processing, and the reaped grain is fed to thegrain tank 6.

The combine is configured such that an engine 8 is provided underneath adriver seat 2 a provided in the driving section 2, and drive forceoutputted by the engine 8 is transmitted to the pair of right and lefttravel apparatuses 1 by a power transmission structure 10 that includesa transmission case 11 provided at the front edge portion of the bodyframe 3.

FIG. 2 is a front view of the schematic structure of the powertransmission structure 10. As shown in this figure, in the powertransmission structure 10, engine drive force from an output shaft 8 aof the engine 8 is inputted to a shift power transmission apparatus 20provided on the side of the upper end portion of the transmission case11 via a power train 12 provided with a power transmission belt 12 a.Output of the shift power transmission apparatus 20 is inputted to atraveling transmission 13 provided inside the transmission case 11, thentransmitted from a left-side steering clutch mechanism 14, which is oneof a pair of right and left steering clutch mechanisms 14 included inthe traveling transmission 13, to a drive shaft 1 a of the left-sidetravel apparatus 1, and also transmitted from the right-side steeringclutch mechanism 14 to a drive shaft 1 a of the right-side travelapparatus 1.

The power transmission structure 10 includes a reaping transmission 15that is provided inside the transmission case 11, and output of theshift power transmission apparatus 20 is inputted to the reapingtransmission 15 and transmitted from a reaping output shaft 16 to adrive shaft 4 f of the reaping section 4.

Next, the shift power transmission apparatus 20 will be described.

As shown in FIGS. 3 and 4, the shift power transmission apparatus 20 isconfigured to include a planetary shift section 20A, which is providedwith a shift case 21 whose side portion is coupled to the upper end sideof the transmission case 11, and a hydraulic continuously variabletransmission 30 that has a casing 31 coupled to the side portion on theside opposite to the side on which the shift case 21 is coupled to thetransmission case 11.

The shift case 21 is configured to include a main case portion 21 a thataccommodates a planetary power transmission section 40 and a power train50, and a coupling case portion 21 b that accommodates a connectionportion between the hydraulic continuously variable transmission 30 andan input shaft 22 and a power transmission shaft 23, and that couplesthe shift case 21 with a port block 34 of the casing 31. The shift case21 is coupled to the transmission case 11 with a bulging portion 21 cformed so as to bulge outward horizontally on the side face of the lowerportion of the main case portion 21 a where the output rotary member 24is located. The size of the coupling case portion 21 b in the up/downdirection of the traveling body is smaller than the size of the maincase portion 21 a in the up/down direction of the traveling body. Themain case portion 21 a is formed such that the shape in vertical sectionis vertically elongated when viewed in the front/rear direction of theapparatus body, the casing 31 is formed such that the shape in verticalsection is vertically elongated when viewed in the front/rear directionof the apparatus body, the planetary shift section 20A and the hydrauliccontinuously variable transmission 30 are aligned in the horizontaldirection of the apparatus body such that the shift power transmissionapparatus 20 has a small width overall in the horizontal direction ofthe apparatus body, and the shift power transmission apparatus 20 iscoupled to the lateral side of the transmission case 11 in a compactstate with respect to the left/right direction of the traveling body soas to not protrude outward horizontally. Furthermore, the side face ofthe lower portion of the casing 31 is formed so as to have an inclinedface 31A that is inclined toward the interior of the apparatus in thedownward direction. A bulging portion 31B that supports a bearing of amotor shaft 33A is formed on the inclined face 31A, thus making theshift power transmission apparatus 20 even more compact. Also, an oilfilter 20F is arranged facing upward on the upper face of the casing 31,and further compactness is achieved by preventing the oil filter 20Ffrom protruding outward horizontally.

The planetary shift section 20A includes the input shaft 22 that isoriented in the horizontal direction of the apparatus body and isrotatably supported to the upper end side of the shift case 21, a powertransmission shaft 23 and a rotating shaft-type of output rotary member24 that are rotatably supported to the lower end side of the shift case21 parallel or substantially parallel to the input shaft 22, theplanetary power transmission section 40 that is supported to the powertransmission shaft 23, and the power train 50 provided so as to spanfrom the input shaft 22 to a carrier 41 of the planetary powertransmission section 40.

The input shaft 22 is arranged so as to be coaxially aligned with a pumpshaft 32 a of the hydraulic continuously variable transmission 30. Theinput shaft 22 is configured such that on the side on which it protrudeslaterally outward from the shift case 21, it is coupled with an outputshaft 8 a of the engine 8 via the power train 12, and on the sideopposite to the side coupled to the engine 8, it is coupled to the pumpshaft 32 a of the hydraulic continuously variable transmission 30 so asto be capable of in-unison rotation therewith via a joint 22 a. Theinput shaft 22 receives engine drive force via the power train 12, anddrives the hydraulic pump 32 of the hydraulic continuously variabletransmission 30 upon being driven by engine drive force.

The output rotary member 24 is arranged so as to be coaxially alignedwith a motor shaft 33 a of the hydraulic continuously variabletransmission 30 on the same side of the hydraulic continuously variabletransmission 30 as the side on which the engine-coupled side of theinput shaft 22 is located. The output rotary member 24 is configuredsuch that on the side on which it protrudes laterally outward from theshift case 21, it is interlocked with an input portion of the travelingtransmission 13, and outputs drive force from the planetary powertransmission section 40 and the hydraulic continuously variabletransmission 30 to the pair of right and left travel apparatuses 1 viathe traveling transmission 13.

The hydraulic continuously variable transmission 30 is configured toinclude the hydraulic pump 32 whose pump shaft 32 a is rotatablysupported to the upper end side of the casing 31, and the hydraulicmotor 33 whose motor shaft 33 a is rotatably supported to the lower endside of the casing 31. The hydraulic pump 32 is configured by a variabledisplacement axial plunger pump, and the hydraulic motor 33 isconfigured by an axial plunger motor. The hydraulic motor 33 is drivenby hydraulic oil that is discharged from the hydraulic pump 32 andsupplied via an oil path formed inside the port block 34. The hydrauliccontinuously variable transmission 30 is supplied with replenishinghydraulic oil by a charge pump 90 mounted to an end portion of the pumpshaft 32 a. The charge pump 90 includes a rotor 90 a attached to thepump shaft 32 a so as to be capable of in-unison rotation therewith, anda pump casing 90 b that is removably coupled to the casing 31.

Accordingly, the hydraulic continuously variable transmission 30switches between the forward power transmission state, the reverse powertransmission state, and the neutral state by an operation for changingthe angle of a swash plate 32 b that the hydraulic pump 32 is providedwith. When the hydraulic continuously variable transmission 30 isswitched to the forward power transmission state, engine drive forcetransmitted from the input shaft 22 to the pump shaft 32 a is convertedinto forward drive force and output from the motor shaft 33 a, and whenit is switched to the reverse power transmission state, engine driveforce transmitted from the input shaft 22 to the pump shaft 32 a isconverted into reverse drive force and output from the motor shaft 33 a,and thus engine drive force is subjected to stepless speed changing andoutput in both the forward power transmission state and the reversepower transmission state. When the hydraulic continuously variabletransmission 30 is switched to the neutral state, output from the motorshaft 33 a is stopped.

The planetary power transmission section 40 is arranged so as to belocated between the motor shaft 33 a and the output rotary member 24 onthe same side of the hydraulic continuously variable transmission 30 asthe side on which the engine-coupled side of the input shaft 22 islocated. The planetary power transmission section 40 includes a sun gear42 that is supported to the power transmission shaft 23, multiple planetgears 43 that are meshed with the sun gear 42, a ring gear 44 that ismeshed with the planet gears 43, and a carrier 41 that rotatablysupports the planet gears 43. The carrier 41 includes arm portions 41 athat rotatably support the planet gears 43 with an extending endportion, and a tube shaft portion 41 b that is coupled to base sides ofthe arm portions 41 a, and the carrier 41 is rotatably supported to thepower transmission shaft 23 with the tube shaft portion 41 b via abearing.

The power transmission shaft 23 and the motor shaft 33 a are coupled toeach other via a joint 23 a so as to be capable of in-unison rotation,the power transmission shaft 23 and the sun gear 42 are coupled via aspline structure so as to be capable of in-unison rotation, and the sungear 42 is interlocked with the motor shaft 33 a so as to be capable ofin-unison rotation.

The ring gear 44 and the output rotary member 24 are interlocked so asto be capable of in-unison rotation, using an annular planet-sideinterlocking member 26 and an annular output-side interlocking member 27that are aligned axially with the power transmission shaft 23 and fitaround it so as to be capable of relative rotation. Specifically, theplanet-side interlocking member 26 includes multiple engaging armportions 26 a that extend radially from the outer circumferentialportion of the planet-side interlocking member 26 so as to be capable ofin-unison rotation. The engaging arm portions 26 a are engaged with thering gear 44 at multiple locations, and the planet-side interlockingmember 26 is interlocked with the ring gear 44 so as to be capable ofin-unison rotation. The output-side interlocking member 27 is engagedwith the planet-side interlocking member 26 using an engaging claw 27 aso as to be capable of in-unison rotation, is engaged with the outputrotary member 24 using a spline structure so as to be capable ofin-unison rotation, and is coupled to the planet-side interlockingmember 26 and the output rotary member 24 so as to be capable ofin-unison rotation. The planet-side interlocking member 26 is supportedto the power transmission shaft 23 via a bearing so as to be capable ofrelative rotation. The output-side interlocking member 27 is rotatablysupported to the shift case 21 via a bearing.

The power train 50 is configured to include a power transmission gear 52that is supported to the input shaft 22 via a needle bearing so as to becapable of relative rotation in a state of being meshed with an inputgear 41 c of the carrier 41 that is provided so as to be capable ofin-unison rotation with the tube shaft portion 41 b of the carrier 41,and an input-side clutch mechanism 55 provided so as to span between thepower transmission gear 52 and the input shaft 22.

The input-side clutch mechanism 55 is configured to include a clutchmember 56 supported to the input shaft 22 so as to be capable ofin-unison rotation and sliding, and a clutch mechanism body 57 providedso as to span between one end side of the clutch member 56 and a lateralside of the power transmission gear 52. The clutch member 56 is causedto slide by a hydraulic piston 58 that is fit inside an end portion ofthe clutch member 56. The clutch mechanism body 57 is configured as ameshing clutch that switches between an on state and an off state when ameshing claw provided on the clutch member 56 and a meshing clawprovided on the power transmission gear 52 engage/disengage with eachother.

When the clutch mechanism body 57 is switched to the on state, theinput-side clutch mechanism 50 is switched to the on state such that theinput shaft 22 and the power transmission gear 52 are interlocked so asto be capable of in-unison rotation, and the carrier 41 of the planetarypower transmission section 40 is switched to the interlocking-on statewith respect to the input shaft 22.

When the clutch mechanism body 57 is switched to the off state, theinput-side clutch mechanism 50 is switched to the off state such thatthe interlocking of the input shaft 22 and the power transmission gear52 is cut off, and the carrier 41 of the planetary power transmissionsection 40 is switched to the interlocking-off state with respect to theinput shaft 22.

Accordingly, in the planetary power transmission section 40, when theinput-side clutch mechanism 50 is switched to the on state, drive forcefrom the input shaft 22 is inputted from a site located between theengine-coupled side and the continuously variable transmission-coupledside of the input shaft 22 to the carrier 41 via the power train 50.When the input-side clutch mechanism 50 is switched to the off state,the planetary power transmission section 40 enters a state in whichinterlocking with the input shaft 22 is cut off.

An output-side clutch mechanism 60 that includes a clutch member 61 fitaround the power transmission shaft 23 is provided so as to span betweenthe sun gear 42 of the planetary power transmission section 40 and theplanet-side interlocking member 26.

When hydraulic oil is supplied to an oil chamber formed on the innercircumferential side of the clutch member 61, the clutch member 61switches to an off position by being caused to slide toward the sun gear42 in resistance to an on biasing spring 62, and when hydraulic oil isdischarged from the oil chamber, the clutch member 61 switches to an onposition by being caused to slide toward the planet-side interlockingmember 26 by the on biasing spring 62. When the clutch member 61switches to the on position, a clutch claw 61 a provided on the clutchmember 61 engages with a clutch claw provided on the planet-sideinterlocking member 26, and thus the clutch member 61 is coupled to theplanet-side interlocking member 26 so as to be capable of in-unisonrotation. The clutch member 61 is caused to slide while maintaining thestate of being engaged with the sun gear 42 so as to be capable ofin-unison rotation by the engaging claw 61 b, and reaches the onposition while maintaining the engaged state with respect to the sungear 42. When the clutch member 61 switches to the off position, theengagement with the planet-side interlocking member 26 using the clutchclaw 61 a is canceled.

Accordingly, with the output-side clutch mechanism 60, when the clutchmember 61 is switched to the off position, the interlocking between thesun gear 42 and the planet-side interlocking member 26 is cut off, thuscutting off the interlocking of the motor shaft 33 a to the outputrotary member 24, and this achieves a first power transmission state inwhich the ring gear 44 of the planetary power transmission section 40and the output rotary member 24 are interlocked so as to be capable ofin-unison rotation, thus enabling combined drive force from theplanetary power transmission section 40 to be output from the outputrotary member 24.

With the output-side clutch mechanism 60, when the clutch member 61 isswitched to the on position, the sun gear 42 and the planet-sideinterlocking member 26 are interlocked so as to be capable of in-unisonrotation, and this achieves a second power transmission state in whichthe motor shaft 33 a is interlocked with the output rotary member 24 soas to be capable of in-unison rotation, thus enabling output from thehydraulic continuously variable transmission 30 to be output from theoutput rotary member 24. Also, when the sun gear 42 and the powertransmission shaft 23 are interlocked so as to be capable of in-unisonrotation, and the ring gear 44 and the planet-side interlocking member26 are interlocked so as to be capable of in-unison rotation, the sungear 42, the planet gears 43, and the ring gear 44 can rotate in unisonwith the motor shaft 33 a such that autorotation of the planet gears 43does not occur.

The output-side clutch mechanism 60 switches the sun gear 43 of theplanetary power transmission section 40 and the output rotary member 24between the interlocking-on state and the interlocking-off state whilemaintaining the interlocked state between the ring gear 44 of theplanetary power transmission section 40 and the output rotary member 24.

Accordingly, with the planetary power transmission section 40, when theinput-side clutch mechanism 55 is switched to the on state, and theoutput-side clutch mechanism 60 is switched to the off state, driveforce from the input shaft 22 is inputted to the carrier 41 via thepower train 50, output from the motor shaft 33 a of the hydrauliccontinuously variable transmission 30 is inputted to the sun gear 42 viathe power transmission shaft 23, drive force from the input shaft 22 andoutput from the hydraulic continuously variable transmission 30 arecombined to generate combined drive force, and the generated combineddrive force is outputted from the ring gear 44 to the output rotarymember 24 via the planet-side interlocking member 26 and the output-sideinterlocking member 27.

A power transmission switching clutch mechanism 70 is configured toinclude the input-side clutch mechanism 55 and the output-side clutchmechanism 60. The power transmission switching clutch mechanism 70switches between a single power transmission state and a combined powertransmission state when the input-side clutch mechanism 55 and theoutput-side clutch mechanism 60 are switched.

FIG. 5 is an illustrative diagram showing the relationship that theoperation states of the input-side clutch mechanism 55 and theoutput-side clutch mechanism 60, the operation state of the powertransmission switching clutch mechanism 70, and the power transmissionmode of the shift power transmission apparatus 20 have with each other.In FIG. 5, “OFF” indicates the off state of the input-side clutchmechanism 55 and the output-side clutch mechanism 60, and “ON” indicatesthe on state of the input-side clutch mechanism 55 and the output-sideclutch mechanism 60. As shown in this figure, the power transmissionswitching clutch mechanism 70 switches to the single power transmissionstate when the input-side clutch mechanism 55 is switched to the offstate and the output-side clutch mechanism 60 is switched to the onstate, and switches to the combined power transmission state when theinput-side clutch mechanism 55 is switched to the on state and theoutput-side clutch mechanism 60 is switched to the off state.

FIG. 3 is a front view in vertical section showing the shift powertransmission apparatus 20 during HMT (Hydraulic Mechanical Transmission)mode power transmission. As shown in this figure, when the powertransmission switching clutch mechanism 70 switches to the combinedpower transmission state, this achieves HMT mode power transmission inthe shift power transmission apparatus 20, in which drive force from theinput shaft 22 and output from the hydraulic continuously variabletransmission 30 are combined by the planetary power transmission section40, and combined drive force from the planetary power transmissionsection 40 is transmitted to the output rotary member 24. When the shiftpower transmission apparatus 20 enters the HMT mode power transmissionstate, engine drive force input to the input shaft 22 is subjected tospeed change by both the hydraulic continuously variable transmission 30and the planetary power transmission section 40, and the speed-changeddrive force is transmitted from the ring gear 44 to the output rotarymember 24, and transmitted from the output rotary member 24 to the pairof right and left travel apparatuses 1.

FIG. 4 is a front view in vertical section showing the shift powertransmission apparatus 20 during HST (Hydraulic Static Transmission)mode power transmission. As shown in this figure, when the powertransmission switching clutch mechanism 70 switches to the single powertransmission state, this achieves HST mode power transmission in theshift power transmission apparatus 20, in which output from thehydraulic continuously variable transmission 30 is transmitted on itsown to the output rotary member 24 without being subjected to speedchange by the planetary power transmission section 40. When the shiftpower transmission apparatus 20 enters the HST mode power transmissionstate, engine drive force is subjected to speed change by only thehydraulic continuously variable transmission 30 and not subjected tospeed change by the planetary power transmission section 40, and thespeed-change drive force is transmitted from the motor shaft 33 a to theoutput rotary member 24 via the power transmission shaft 23, the sungear 42, the clutch member 61, the planet-side interlocking member 26,and the output-side interlocking member 27, and then transmitted fromthe output rotary member 24 to the pair of right and left travelapparatuses 1.

With the power transmission switching clutch mechanism 70, if the shiftpower transmission apparatus 20 is put in the HST mode powertransmission state, power transmission from the input shaft 22 to thecarrier 41 of the planetary power transmission section 40 is cut off,the sun gear 42 is interlocked with the motor shaft 33 a via the powertransmission shaft 23 so as to be capable of in-unison rotation, and thering gear 44 is interlocked with the motor shaft 33 a via theplanet-side interlocking member 26, the clutch member 61, the sun gear42, and the power transmission shaft 23 so as to be capable of in-unisonrotation, and therefore the sun gear 42, the planet gears 43, and thering gear 44 of the planetary power transmission section 40 operate soas to rotate in unison with the motor shaft 33 a. Accordingly, if theshift power transmission apparatus 20 is put in the state in which HSTmode power transmission is realized, output from the motor shaft 33 a ofthe hydraulic continuously variable transmission 30 is transmitted tothe output rotary member 24 without autorotation of the planet gears 43occurring, that is to say, without relative rotation of the sun gear 42and the planet gears 43 or relative rotation of the planet gears 43 andthe ring gear 44 occurring.

FIG. 6 is an illustrative diagram showing the relationship between theshift state of the hydraulic continuously variable transmission 30 andthe output speed of the output rotary member 24 of the shift powertransmission apparatus 20 in the state in which the accelerator of theengine 8 is set such that a set constant speed of drive force is output.In FIG. 6, the horizontal axis indicates the shift state of thehydraulic continuously variable transmission 30, “n” indicates theneutral position of the hydraulic continuously variable transmission 30,“−max” indicates the maximum speed position in the reverse powertransmission state of the hydraulic continuously variable transmission30, and “+max” indicates the maximum speed position in the forward powertransmission state of the hydraulic continuously variable transmission30. The vertical axis in FIG. 6 indicates the output speed of the outputrotary member 24. A solid line R and a solid line FL shown in FIG. 6indicate change in the output speed when the input-side clutch mechanism55 is in the off state, and the output-side clutch mechanism 60 is inthe on state, that is to say, when the shift power transmissionapparatus 20 is put in the HST mode power transmission state. A solidline FH shown in FIG. 6 indicates change in the output speed when theinput-side clutch mechanism 55 is in the on state, and the output-sideclutch mechanism 60 is in the off state, that is to say, when the shiftpower transmission apparatus 20 is put in the HMT mode powertransmission state.

As shown by the solid line R and the solid line FL, in the state wherethe input-side clutch mechanism 55 is maintained in the off state andthe output-side clutch mechanism 60 is maintained in the on state, ifthe hydraulic continuously variable transmission 30 is operated to themaximum speed position “−max” in the reverse power transmission state,the output speed reaches the reverse maximum speed “RVH”. As thehydraulic continuously variable transmission 30 is shifted from themaximum speed position “−max” in the reverse power transmission statetoward the neutral position “n”, the reverse output speed steplesslydecreases. When the hydraulic continuously variable transmission 30reaches the neutral position “n”, the output speed reaches zero “0”. Asthe hydraulic continuously variable transmission 30 is shifted from theneutral position “n” toward the maximum speed position “+max” in theforward power transmission state, the forward output speed steplesslyincreases. When the hydraulic continuously variable transmission 30reaches the maximum speed position “+max” in the forward powertransmission state, the output speed reaches a forward intermediatespeed “FVM”.

As shown by the solid line FH, when the hydraulic continuously variabletransmission 30 reaches the maximum speed position “+max” in the forwardpower transmission state, the input-side clutch mechanism 55 iscontrolled so as to switch from the off state to the on state, theoutput-side clutch mechanism 60 is controlled so as to switch from theon state to the off state, and in the state in which the input-sideclutch mechanism 55 is maintained in the on state, and the output-sideclutch mechanism 60 is maintained in the off state, as the hydrauliccontinuously variable transmission 30 is shifted from the maximum speedposition “+max” in the forward power transmission state toward themaximum speed position “−max” in the reverse power transmission state,the forward output speed steplessly increases. When the hydrauliccontinuously variable transmission 30 reaches the maximum speed position“+max” in the reverse power transmission state, the forward output speedreaches the maximum speed “FVH”.

In FIG. 6, “N” indicates the value on the horizontal axis when the solidline FH extends beyond the forward-side maximum speed position “+max” ofthe hydraulic continuously variable transmission 30 to the point atwhich the output rotation reaches zero “0”. Letting 1 be the horizontalaxis value for the forward-side maximum speed position “+max” of thehydraulic continuously variable transmission 30, N=1.6 to 2.2. In otherwords, the capacities of the hydraulic pump 32 and the hydraulic motor33 in the hydraulic continuously variable transmission 30 and the powertransmission gear ratio of the planetary power transmission section 40are set such that N=1.6 to 2.2.

FIG. 7 is a block diagram showing a shift operation apparatus 71 thatperforms shift operations on the shift power transmission apparatus 20.As shown in this figure, the shift operation apparatus 71 includes acontrol apparatus 72 that is linked to a shift operation section 30 a ofthe hydraulic continuously variable transmission 30 and operationsections 55 a and 60 a of the input-side clutch mechanism 55 and theoutput-side clutch mechanism 60, as well as a shift detection sensor 73,an engine speed sensor 74, a transmission output speed sensor 75, and anoutput speed sensor 76 that are linked to the control apparatus 72.

The shift operation section 30 a is configured by an electrical actuatoror a hydraulic actuator that operates so as to change the angle of theswash plate 32 b of the hydraulic pump 32 in the hydraulic continuouslyvariable transmission 30. The operation section 55 a of the input-sideclutch mechanism 55 is configured by an operation valve that isconnected to the hydraulic piston 58 via an operation oil path formedinside the input shaft 22, and by operating the hydraulic piston 58 soas to cause the clutch member 56 to slide, the operation section 55 aswitches the input-side clutch mechanism 55. The operation section 60 aof the output-side clutch mechanism 60 is configured by an operationvalve that is connected to the oil chamber of the clutch member 61 viaan operation oil path formed inside the power transmission shaft 23, andby supplying/discharging operation oil to/from the oil chamber of theclutch member 61, the operation section 60 a causes the clutch member 61to slide so as to switch the output-side clutch mechanism 60.

The shift detection sensor 73 detects the operation position of a shiftlever 77, and outputs this detection result to the control apparatus 72.The engine speed sensor 74 detects the rotational speed of the engine 8,and outputs this detection result to the control apparatus 72. Thetransmission output speed sensor 75 detects the output speed of thehydraulic continuously variable transmission 30, and outputs thisdetection result to the control apparatus 72. The output speed sensor 76detects the output speed of the shift power transmission apparatus 20,and outputs this detection result to the control apparatus 72.

The control apparatus 72 is configured using a microcomputer, andincludes a shift control module 78. Based on the detection informationfrom the shift detection sensor 73 and the transmission output speedsensor 75, the shift control module 78 performs shift control on thehydraulic continuously variable transmission by operating the shiftoperation section 30 a such that the shift state of the hydrauliccontinuously variable transmission 30 corresponds to the operationposition of the shift lever 77.

In addition to performing shift control on the hydraulic continuouslyvariable transmission 30, the shift control module 78 detects therotational speed of the engine 8, whose accelerator has been set, basedon the detection information from the engine speed sensor 74, and then,based on this detection result and the detection information from theshift detection sensor 73, the transmission output speed sensor 75, andthe output speed sensor 76, the shift control module 78 performs controlfor operating the operation section 55 a and the operation section 60 aso as to switch the input-side clutch mechanism 55 and the output-sideclutch mechanism 60 in accordance with predetermined timing so that theshift power transmission apparatus 20 transmits power while achievingHST mode power transmission and HMT mode power transmission as shown inFIGS. 5 and 6.

First Alternative Embodiment

FIG. 8 is a front view in vertical section of the shift powertransmission apparatus 20 having a first alternative embodimentstructure. As shown in this figure, the shift power transmissionapparatus 20 having the first alternative embodiment structure includesa forward/reverse switching mechanism 80 provided so as to span betweenthe input shaft 22 and the carrier 41 of the planetary powertransmission section 40.

The shift power transmission apparatus 20 having the first alternativeembodiment structure includes a charge pump 90 mounted at a positionthat is between the engine-coupled side and the hydraulic continuouslyvariable transmission-coupled side of the input shaft 22, and is betweenthe engine-coupled side of the input shaft 22 and a forward clutch 82,and replenishing hydraulic oil is supplied to the hydraulic continuouslyvariable transmission 30 by the charge pump 90. The charge pump 90includes a rotor 90 a that is coupled to the input shaft 22 so as to becapable of in-unison rotation, and a pump casing 90 b that is removablyattached to the shift case 21.

The forward/reverse switching mechanism 80 includes a forward powertransmission gear 81 that is rotatably supported to the input shaft 22via a needle bearing, a forward clutch 82 that is provided so as to spanbetween the power transmission gear 81 and the input shaft 22, a reversepower transmission shaft 83 that is rotatably supported to the shiftcase 21 in an arrangement parallel or substantially parallel to theinput shaft 22, a reverse rotation input gear 85 that is supported tothe reverse power transmission shaft 83 so as to be capable of relativerotation when meshed with a power transmission gear 84 that is supportedto the input shaft 22 so as to be capable of in-unison rotation, areverse clutch 86 that is provided so as to span between the input gear85 and the reverse power transmission shaft 83, and a reverse powertransmission gear 87 that is provided so as to be capable of in-unisonrotation with the reverse power transmission shaft 83.

The forward power transmission gear 81 and the reverse powertransmission gear 87 are meshed with the input gear 41 c of the carrier41 that is provided so as to be capable of in-unison rotation with thetube shaft portion 41 b of the carrier 41. The input gear 85 and thepower transmission gear 84 are located on the side of the planetarypower transmission section 40 opposite to the side on which the forwardpower transmission gear 81 and the reverse power transmission gear 87are located. The forward power transmission gear 81 and the reversepower transmission gear 87 are meshed with the input gear 41 c of theplanetary power transmission section 40 that is located on the side ofthe sun gear 42 opposite to the side on which the input gear 85 and thepower transmission gear 84 are located.

The forward clutch 82 is configured to include a forward clutch member82 a that is supported to the input shaft 22 so as to be capable ofin-unison rotation and sliding, and a clutch mechanism body 82 b that isprovided so as to span between one end side of the forward clutch member82 a and a lateral side of the forward power transmission gear 81. Theforward clutch member 82 a is caused to slide by a hydraulic piston 88fit inside an end portion of the forward clutch member 82 a. The clutchmechanism body 82 b is configured as a meshing clutch that switchesbetween an on state and an off state when a meshing claw provided on theforward clutch member 82 a and a meshing claw provided on the forwardpower transmission gear 81 engage/disengage with each other.

The reverse clutch 86 is configured to include a reverse clutch member86 a that is supported to the reverse power transmission shaft 83 so asto be capable of in-unison rotation and sliding, and a clutch mechanismbody 86 b that is provided so as to span between one end side of thereverse clutch member 86 a and a lateral side of the input gear 85. Thereverse clutch member 86 a is caused to slide by a hydraulic piston 89fit inside an end portion of the reverse clutch member 86 a. The clutchmechanism body 86 b is configured as a meshing clutch that switchesbetween an on state and an off state when a meshing claw provided on thereverse clutch member 86 a and a meshing claw provided on the input gear85 engage/disengage with each other.

When the forward clutch 82 is switched to the on state, and the reverseclutch 86 is switched to the off state, the forward/reverse switchingmechanism 80 enters the forward power transmission state, inputs driveforce of the input shaft 22 from the forward clutch member 82 a that islocated between the engine-coupled side and the hydraulic continuouslyvariable transmission-coupled side of the input shaft 22, converts thedrive force from the input shaft 22 into forward drive force, andtransmits it from the forward power transmission gear 81 to the carrier41.

When the forward clutch 82 is switched to the off state, and the reverseclutch 86 is switched to the on state, the forward/reverse switchingmechanism 80 enters the reverse power transmission state, inputs driveforce of the input shaft 22 from the power transmission gear 84 that islocated between the engine-coupled side and the hydraulic continuouslyvariable transmission-coupled side of the input shaft 22, converts thedrive force from the input shaft 22 into reverse drive force, andtransmits it from the reverse power transmission gear 87 to the carrier41 of the planetary power transmission section 40.

When the forward clutch 82 and the reverse clutch 86 are switched to theoff state, the forward/reverse switching mechanism 80 enters the neutralstate and cuts off the interlocking of the input shaft 22 and thecarrier 41 of the planetary power transmission section 40.

FIG. 9 is an illustrative diagram showing the relationship that theoperation states of the hydraulic continuously variable transmission 30,the forward clutch 82, the reverse clutch 86, and the output-side clutchmechanism 60 have with the power transmission mode of the shift powertransmission apparatus 20. In FIG. 9, “forward” indicates the forwardpower transmission state of the hydraulic continuously variabletransmission 30, and “reverse” indicates the reverse power transmissionstate of the hydraulic continuously variable transmission 30. In FIG. 9,“OFF” indicates the off state of the forward clutch 82, the reverseclutch 86, and the output-side clutch mechanism 60, and “ON” indicatesthe on state of the forward clutch 82, the reverse clutch 86, and theoutput-side clutch mechanism 60.

When the forward clutch 82 and the reverse clutch 86 are controlled soas to be switched to the off state, and the output-side clutch mechanism60 is controlled so as to be switched to the on state, the shift powertransmission apparatus 20 enters the state in which HST mode powertransmission is achieved. When the shift power transmission apparatus 20enters the HST mode power transmission state, engine drive force inputby the input shaft 22 is subjected to speed change by the hydrauliccontinuously variable transmission 30 without being transmitted to theplanetary power transmission section 40, the speed-changed drive forceis transmitted from the motor shaft 33 a to the output rotary member 24via the power transmission shaft 23, the sun gear 42, the clutch member61, the planet-side interlocking member 26, and the output-sideinterlocking member 27, and then transmitted from the output rotarymember 24 to the pair of right and left travel apparatuses 1.

When the forward clutch 82 is controlled so as to switch to the onstate, and the reverse clutch 86 and the output-side clutch mechanism 60are controlled so as to switch to the off state, the shift powertransmission apparatus 20 enters a state in which forward-side HMT modepower transmission is achieved. When the shift power transmissionapparatus 20 enters the forward-side HMT mode power transmission state,engine drive force input by the input shaft 20 is converted into forwarddrive force by the forward/reverse switching mechanism 80 andtransmitted to the planetary power transmission section 40, theplanetary power transmission section 40 combines the forward drive forcefrom the forward/reverse switching mechanism 80 with output from themotor shaft 33 a of the hydraulic continuously variable transmission 30so as to generate forward-side combined drive force, and the generatedforward-side combined drive force is transmitted from the ring gear 44to the output rotary member 24 via the planet-side interlocking member26 and the output-side interlocking member 27, and then transmitted fromthe output rotary member 24 to the pair of right and left travelapparatuses 1.

When the reverse clutch 86 is controlled so as to switch to the onstate, and the forward clutch 82 and the output-side clutch mechanism 60are controlled so as to switch to the off state, the shift powertransmission apparatus 20 enters a state in which reverse-side HMT modepower transmission is achieved. When the shift power transmissionapparatus 20 enters the reverse-side HMT mode power transmission state,engine drive force input by the input shaft 20 is converted into reversedrive force by the forward/reverse switching mechanism 80 andtransmitted to the planetary power transmission section 40, theplanetary power transmission section 40 combines the reverse drive forcefrom the forward/reverse switching mechanism 80 with output from themotor shaft 33 a of the hydraulic continuously variable transmission 30so as to generate reverse-side combined drive force, and the generatedreverse-side combined drive force is transmitted from the ring gear 44to the output rotary member 24 via the planet-side interlocking member26 and the output-side interlocking member 27, and then transmitted fromthe output rotary member 24 to the pair of right and left travelapparatuses 1.

FIG. 10 is an illustrative diagram showing the output speed of the shiftpower transmission apparatus 20 having the first alternative embodimentstructure, being an illustrative diagram showing the relationship thatthe shift state of the hydraulic continuously variable transmission 30has with the output speed of the output rotary member 24 of the shiftpower transmission apparatus 20 in the state in which the accelerator ofthe engine 8 is set such that a set constant speed of drive force isoutput. In FIG. 10, the horizontal axis indicates the shift state of thehydraulic continuously variable transmission 30, “n” indicates theneutral position of the hydraulic continuously variable transmission 30,“−max” indicates the maximum speed position in the reverse powertransmission state of the hydraulic continuously variable transmission30, and “+max” indicates the maximum speed position in the forward powertransmission state of the hydraulic continuously variable transmission30. The vertical axis in FIG. 10 indicates the output speed of theoutput rotary member 24. A solid line RL and a solid line FL shown inFIG. 10 indicate change in the output speed when the forward clutch 82and the reverse clutch 86 are controlled so as to switch to the offstate, and the output-side clutch mechanism 60 is controlled so as toswitch to the on state, that is to say, when the shift powertransmission apparatus 20 is put in the HST mode power transmissionstate. Solid lines FM and FH shown in FIG. 10 indicate change in theoutput speed when the forward clutch 82 is controlled so as to switch tothe on state, and the reverse clutch 86 and the output-side clutchmechanism 60 are controlled so as to switch to the off state, that is tosay, when the shift power transmission apparatus 20 is put in theforward-side HMT mode power transmission state. Solid lines RM and RHshown in FIG. 10 indicate change in the output speed when the reverseclutch 86 is controlled so as to switch to the on state, and the forwardclutch 82 and the output-side clutch mechanism 60 are controlled so asto switch to the off state, that is to say, when the shift powertransmission apparatus 20 is put in the reverse-side HMT mode powertransmission state.

As shown in FIG. 9, and as shown by the solid line FL in FIG. 10, in thestate in which the forward clutch 82 and the reverse clutch 86 are inthe off state, and the output-side clutch mechanism 60 is in the onstate, if the hydraulic continuously variable transmission 30 isoperated to the neutral position “n”, the output changes to zero “0”.

While the forward clutch 82 and the reverse clutch 86 are maintained inthe off state, and the output-side clutch mechanism 60 is maintained inthe on state, if the hydraulic continuously variable transmission 30 isshifted from the neutral position “n” toward the maximum speed position“+max” in the forward power transmission state, forward drive force isoutput. While the forward clutch 82 and the reverse clutch 86 aremaintained in the off state, and the output-side clutch mechanism 60 ismaintained in the on state, as the hydraulic continuously variabletransmission 30 is shifted from the neutral position “n” toward themaximum speed position “+max” in the forward power transmission state,forward output steplessly increases. When the hydraulic continuouslyvariable transmission 30 reaches the maximum speed position “+max” inthe forward power transmission state, the output speed reaches a forwardintermediate speed “FV1”.

As shown in FIG. 9, and as shown by the solid lines FM and FH in FIG.10, when the hydraulic continuously variable transmission 30 reaches themaximum speed position “+max” in the forward power transmission state,the forward clutch 82 is controlled so as to switch to the on state, andthe output-side clutch mechanism 60 is controlled so as to switch to theoff state, and, while the forward clutch 82 is maintained in the onstate, and the reverse clutch 86 and the output-side clutch mechanism 60are maintained in the off state, as the hydraulic continuously variabletransmission 30 is shifted from the maximum speed position “+max” in theforward power transmission state toward the maximum speed position“−max” in the reverse power transmission state, the forward outputsteplessly increases from the intermediate speed “FV1”. When thehydraulic continuously variable transmission 30 reaches the maximumspeed position “−max” in the reverse power transmission state, theoutput speed reaches a forward intermediate speed “FV2”.

As shown in FIG. 9, and as shown by the solid line RL in FIG. 10, whilethe forward clutch 82 and the reverse clutch 86 are maintained in theoff state, and the output-side clutch mechanism 60 is maintained in theon state, if the hydraulic continuously variable transmission 30 isshifted from the neutral position “n” toward to the maximum speedposition “−max” in the reverse power transmission state, reverse driveforce is output. While the forward clutch 82 and the reverse clutch 86are maintained in the off state, and the output-side clutch mechanism 60is maintained in the on state, as the hydraulic continuously variabletransmission 30 is shifted from the neutral position “n” toward themaximum speed position “−max” in the reverse power transmission state,the reverse output steplessly increases. When the hydraulic continuouslyvariable transmission 30 reaches the maximum speed position “−max” inthe reverse power transmission state, the output speed reaches a reverseintermediate speed “RV1”.

As shown in FIG. 9, and as shown by the solid lines RM and RH in FIG.10, when the hydraulic continuously variable transmission 30 reaches themaximum speed position “−max” in the reverse power transmission state,the reverse clutch 86 is controlled so as to switch to the on state, andthe output-side clutch mechanism 60 is controlled so as to switch to theoff state, and, while the reverse clutch 86 is maintained in the onstate, and the forward clutch 82 and the output-side clutch mechanism 60are maintained in the off state, as the hydraulic continuously variabletransmission 30 is shifted from the maximum speed position “−max” in thereverse power transmission state toward the maximum speed position“+max” in the forward power transmission state, the reverse outputsteplessly increases from the intermediate speed “RV1”. When thehydraulic continuously variable transmission 30 reaches the maximumspeed position “+max” in the forward power transmission state, theoutput reaches a reverse intermediate speed “RV2”.

In FIG. 10, “N” indicates the value on the horizontal axis when thesolid lines FH and FM extend beyond the forward-side maximum speedposition “+max” of the hydraulic continuously variable transmission 30to the point at which the output rotation reaches zero “0”. Letting 1 bethe horizontal axis value for the forward-side maximum speed position“+max” of the hydraulic continuously variable transmission 30, N=1.6 to2.2. In other words, the capacities of the hydraulic pump 32 and thehydraulic motor 33 in the hydraulic continuously variable transmission30 and the power transmission gear ratio of the planetary powertransmission section 40 are set such that N=1.6 to 2.2.

FIG. 11 is a block diagram showing a shift operation apparatus 91 thatperforms shift operations on the shift power transmission apparatus 20having the first alternative embodiment structure. As shown in thisfigure, the shift operation apparatus 91 includes a control apparatus 72that is linked to the shift operation section 30 a of the hydrauliccontinuously variable transmission 30 and operation sections 82 c, 86 c,and 60 a of the forward clutch 82, the reverse clutch 86, and theoutput-side clutch mechanism 60, as well as the shift detection sensor73, the engine speed sensor 74, the transmission output speed sensor 75,and the output speed sensor 76 that are linked to the control apparatus72.

The shift operation section 30 a is configured by an electrical actuatoror a hydraulic actuator that operates so as to change the angle of theswash plate 32 b of the hydraulic pump 32 in the hydraulic continuouslyvariable transmission 30. The operation section 82 c of the forwardclutch 82 is configured by an operation valve that is connected to ahydraulic piston 88 via an operation oil path formed inside the inputshaft 22, and by operating the hydraulic piston 88 so as to cause theforward clutch member 82 a to slide, the operation section 82 c switchesthe forward clutch 82. The operation section 86 c of the reverse clutch86 is configured by an operation valve that is connected to a hydraulicpiston 89 via an operation oil path formed inside the reverse powertransmission shaft 83, and by operating the hydraulic piston 89 so as tocause the reverse clutch member 86 a to slide, the operation section 86c switches the reverse clutch 86. The operation section 60 a of theoutput-side clutch mechanism 60 is configured by an operation valve thatis connected to the oil chamber of the clutch member 61 via an operationoil path formed inside the power transmission shaft 23, and bysupplying/discharging operation oil to/from the oil chamber of theclutch member 61, the operation sectiont 60 a causes the clutch member61 to slide so as to switch the output-side clutch mechanism 60.

The shift detection sensor 73 detects the operation position of a shiftlever 77, and outputs this detection result to the control apparatus 72.The engine speed sensor 74 detects the rotational speed of the engine 8,and outputs this detection result to the control apparatus 72. Thetransmission output speed sensor 75 detects the output speed of thehydraulic continuously variable transmission 30, and outputs thisdetection result to the control apparatus 72. The output speed sensor 76detects the output speed of the shift power transmission apparatus 20,and outputs this detection result to the control apparatus 72.

The control apparatus 72 is configured using a microcomputer, andincludes a shift control module 78. Based on the detection informationfrom the shift detection sensor 73 and the transmission output speedsensor 75, the shift control module 78 performs shift control on thehydraulic continuously variable transmission by operating the shiftoperation section 30 a such that the shift state of the hydrauliccontinuously variable transmission 30 corresponds to the operationposition of the shift lever 77.

In addition to performing shift control on the hydraulic continuouslyvariable transmission 30, the shift control module 78 detects therotational speed of the engine 8, whose accelerator has been set, basedon the detection information from the engine speed sensor 74, and then,based on this detection result and the detection information from theshift detection sensor 73, the transmission output speed sensor 75, andthe output speed sensor 76, the shift control module 78 performs controlfor operating the operation section 82 c, the operation section 86 c,and the operation section 60 a so as to switch the forward clutch 82,the reverse clutch 86, and the output-side clutch mechanism 60 inaccordance with predetermined timing so that the shift powertransmission apparatus 20 transmits power while achieving HST mode powertransmission, forward-side HMT mode power transmission, and reverse-sideHMT mode power transmission as shown in FIGS. 9 and 10.

Second Alternative Embodiment

FIG. 12 is a front view in vertical section of the shift powertransmission apparatus 20 having a second alternative embodimentstructure. As shown in this figure, in the shift power transmissionapparatus 20 having the second alternative embodiment structure, thecharge pump 90 that supplies replenishing hydraulic oil to the hydrauliccontinuously variable transmission 30 is mounted at a position that isbetween the engine-coupled side and the hydraulic continuously variabletransmission-coupled side of the input shaft 22, and is between theengine-coupled side of the input shaft 22 and the input-side clutchmechanism 55. The charge pump 90 includes the rotor 90 a that is coupledto the input shaft 22 so as to be capable of in-unison rotation, and thepump casing 90 b that is removably coupled to the shift case 21.

Third Alternative Embodiment

FIG. 13 is a front view in vertical section of the shift powertransmission apparatus 20 having a third alternative embodimentstructure. As shown in this figure, in the shift power transmissionapparatus 20 having the third alternative embodiment structure, thehydraulic continuously variable transmission 30 is configured to includea variable displacement hydraulic pump 32 and a variable displacementhydraulic motor 33.

Fourth Alternative Embodiment

FIG. 14 is a front view in vertical section of the shift powertransmission apparatus 20 having a fourth alternative embodimentstructure. As shown in this figure, in the shift power transmissionapparatus 20 having the fourth alternative embodiment structure, theoutput-side clutch mechanism 60 is configured as a friction-type clutchmechanism that includes a multi-disc friction clutch portion 64 providedso as to span between a support member 63 that is provided on the powertransmission shaft 23 so as to be capable of in-unison rotation and aclutch body portion provided on the planet-side interlocking member 26.This output-side clutch mechanism 60 operates so as to switch the motorshaft 33 a and the output rotary member 24 between the interlocking-onstate and the interlocking-off state when the friction clutch portion 64is switched between the on state and the off state by a hydraulic piston65 supported to the sun gear 42.

Fifth Alternative Embodiment

FIG. 15 is a front view in vertical section of the shift powertransmission apparatus 20 having a fifth alternative embodimentstructure. As shown in this figure, in the shift power transmissionapparatus 20 having the fifth alternative embodiment structure, theinput-side clutch mechanism 55 is configured as a friction-type clutchmechanism that includes a multi-disc friction clutch portion 59 providedso as to span between a support portion that is provided on the powertransmission gear 52 so as to be capable of in-unison rotation and aclutch body portion 59 a provided on the input shaft 22 so as to becapable of in-unison rotation. This input-side clutch mechanism 55operates so as to switch the input shaft 22 and the power transmissiongear 52 between the interlocking-on state and the interlocking-off statewhen the friction clutch portion 59 is switched between the on state andthe off state by a hydraulic piston 59 b provided inside the clutch bodyportion 59 a.

Sixth Alternative Embodiment

FIG. 16 is a front view in vertical section of the shift powertransmission apparatus 20 having a sixth alternative embodimentstructure. As shown in this figure, in the shift power transmissionapparatus 20 having the sixth alternative embodiment structure, theoutput-side clutch mechanism 60 is configured as a friction-type clutchmechanism that includes a multi-disc friction clutch portion 67 providedso as to span between a support portion 66 that is provided on the powertransmission shaft 23 so as to be capable of in-unison rotation and aclutch body 67 a coupled to the output-side interlocking member 27 so asto be capable of in-unison rotation. This output-side clutch mechanism60 operates so as to switch the motor shaft 33 a and the output rotarymember 24 between the interlocking-on state and the interlocking-offstate when the friction clutch portion 67 is switched between the onstate and the off state by a hydraulic piston 67 b provided inside theclutch body 67 a.

The shift power transmission apparatus 20 having the sixth alternativeembodiment structure includes a friction clutch mechanism 79 that canswitch the ring gear 44 and the motor shaft 33 a between theinterlocking-on state and the interlocking-off state, and it is possibleto switch between a state in which the sun gear 42, the planet gears 43,and the ring gear 44 rotate in unison with the motor shaft 33 a in HSTmode power transmission, and a state in which the ring gear 44 canrotate in HST mode power transmission.

Other Alternative Embodiments

(1) Although the above-described embodiment gives the example wheredrive force from the input shaft 22 is inputted to the carrier 41 of theplanetary power transmission section 40, and drive force from the ringgear 44 of the planetary power transmission section 40 is transmitted tothe output rotary member 24, a configuration may be implemented in whichdrive force from the input shaft 22 is inputted to the ring gear 44 ofthe planetary power transmission section 40, and drive force from thecarrier 41 of the planetary power transmission section 40 is transmittedto the output rotary member 24.

(2) Although the above-described embodiment gives the example where theinput shaft 22 is formed so as to be separate from the pump shaft 32 aand is coupled to the pump shaft 32 a via the joint 22 a, and the powertransmission shaft 23 is formed so as to be separate from the motorshaft 33 a and is coupled to the motor shaft 33 a via the joint 23 a, animplementation is possible in which the input shaft 22 is formedintegral with the pump shaft 32 a, and the power transmission shaft 23is formed integral with the motor shaft 33 a.

Second Embodiment

Next, a second embodiment will be described with reference to FIGS. 17to 25.

As shown in FIG. 17, the combine, which performs the task of harvestingrice, barley, and the like, is configured to be self-propelled with apair of right and left crawling travel apparatuses 101, and isconfigured to include a traveling body equipped with a riding drivingsection 102, a reaping section 104 coupled to the front portion of abody frame 103 of the traveling body, a threshing apparatus 105 providedso as to be arranged rearward of the reaping section 104 on the rearside of the body frame 103, and a grain tank 106 provided so as to bearranged to the side of the threshing apparatus 105 on the rear side ofthe body frame 103.

Specifically, the reaping section 104 includes a reaping section frame104 a that extends forward from the front portion of the body frame 103in a vertically swingable manner, and when the reaping section frame 104a is swung by an elevating cylinder 107, the reaping section 104 movesup/down between a lowered operating position at which a divider 104 b,which is provided at the front edge portion of the reaping section 104,is lowered close to the ground, and a raised non-operating position atwhich the divider 104 b is raised high above the ground. When thetraveling body is caused to travel with the reaping section 104 loweredto the lowered operating position, the reaping section 104 operates suchthat reaping-target planted stalks are guided to a raising path by thedivider 104 b, the planted stalks that were guided to the raising pathare reaped by a clipper-type reaping apparatus 104 d while being raisedup by a raising apparatus 104 c, and the reaped stalks are supplied tothe threshing apparatus 105 by a supplying apparatus 104 e. In thethreshing apparatus 105, the reaped stalks are conveyed from thesupplying apparatus 104 e toward the rear of the apparatus body withtheir base sides clamped by a threshing feed chain 105 a, the eartip-sides of the reaped stalks are supplied to a handling compartment(not shown) where they are subjected to reaping processing, and thereaped grain is fed to the grain tank 106.

The combine is configured such that an engine 108 is provided underneatha driver seat 102 a provided in the driving section 102, and drive forceoutputted by the engine 108 is transmitted to the pair of right and lefttravel apparatuses 101 by a power transmission structure 110 thatincludes a transmission case 111 provided at the front edge portion ofthe body frame 103.

FIG. 18 is a front view of the schematic structure of the powertransmission structure 110. As shown in this figure, in the powertransmission structure 110, engine drive force from an output shaft 108a of the engine 108 is inputted to a shift power transmission apparatus120 provided on the side of the upper end portion of the transmissioncase 111 via a power train 112 provided with a power transmission belt112 a. Output of the shift power transmission apparatus 120 is inputtedto a traveling transmission 113 provided inside the transmission case111, then transmitted from a left-side steering clutch mechanism 114,which is one of a pair of right and left steering clutch mechanisms 114included in the traveling transmission 113, to a drive shaft 101 a ofthe left-side travel apparatus 101, and also transmitted from theright-side steering clutch mechanism 114 to a drive shaft 101 a of theright-side travel apparatus 101.

The power transmission structure 110 includes a reaping transmission 115that is provided inside the transmission case 111, and output of theshift power transmission apparatus 120 is inputted to the reapingtransmission 115 and transmitted from a reaping output shaft 116 to adrive shaft 104 f of the reaping section 104.

Next, the shift power transmission apparatus 120 will be described.

As shown in FIG. 19, the shift power transmission apparatus 120 isconfigured to include a planetary shift section 120A, which is providedwith a shift case 121 whose side portion is coupled to the upper endside of the transmission case 111, and a hydraulic continuously variabletransmission 130 that has a casing 131 coupled to the side portion onthe side opposite to the side on which the shift case 121 is coupled tothe transmission case 111.

The shift case 121 is configured to include a main case portion 121 athat accommodates a planetary power transmission section 140 and aforward/reverse switching mechanism 150, and a coupling case portion 121b that accommodates a connection portion between the hydrauliccontinuously variable transmission 130 and an input shaft 122 and apower transmission shaft 123, and that couples the shift case 121 with aport block 134 of the casing 131. The shift case 121 is coupled to thetransmission case 111 with a bulging portion 121 c formed so as to bulgeoutward horizontally on the side face of the lower portion of the maincase portion 121 a where the output rotary member 124 is located. Thesize of the coupling case portion 121 b in the up/down direction of thetraveling body is smaller than the size of the main case portion 121 ain the up/down direction of the traveling body. The main case portion121 a is formed such that the shape in vertical section is verticallyelongated when viewed in the front/rear direction of the apparatus body,the casing 131 is formed such that the shape in vertical section isvertically elongated when viewed in the front/rear direction of theapparatus body, the planetary shift section 120A and the hydrauliccontinuously variable transmission 130 are aligned in the horizontaldirection of the apparatus body such that the shift power transmissionapparatus 120 has a small width overall in the horizontal direction ofthe apparatus body, and the shift power transmission apparatus 120 iscoupled to the lateral side of the transmission case 111 in a compactstate with respect to the left/right direction of the traveling body soas to not protrude outward horizontally. Also, an oil filter 120F isarranged facing upward on the upper face of the casing 131, and furthercompactness is achieved by preventing the oil filter 120F fromprotruding outward horizontally.

The planetary shift section 120A includes the input shaft 122 that isoriented in the horizontal direction of the apparatus body and isrotatably supported to the upper end side of the shift case 121, a powertransmission shaft 123 and a rotating shaft-type of output rotary member124 that are rotatably supported to the lower end side of the shift case121 parallel or substantially parallel to the input shaft 122, theplanetary power transmission section 140 that is supported to the powertransmission shaft 123, and the forward/reverse switching mechanism 150provided so as to span from the input shaft 122 to a carrier 141 of theplanetary power transmission section 140.

The input shaft 122 is arranged so as to be coaxially aligned with apump shaft 132 a of the hydraulic continuously variable transmission130. The input shaft 122 is configured such that on the side on which itprotrudes laterally outward from the shift case 121, it is coupled withan output shaft 108 a of the engine 108 via the power train 112, and onthe side opposite to the side coupled to the engine 108, it is coupledto the pump shaft 132 a of the hydraulic continuously variabletransmission 130 so as to be capable of in-unison rotation therewith viaa joint 122 a. The input shaft 122 receives engine drive force via thepower train 112, and drives the hydraulic pump 132 of the hydrauliccontinuously variable transmission 130 upon being driven by engine driveforce.

The output rotary member 124 is arranged so as to be coaxially alignedwith a motor shaft 133 a of the hydraulic continuously variabletransmission 130 on the same side of the hydraulic continuously variabletransmission 130 as the side on which the engine-coupled side of theinput shaft 122 is located. The output rotary member 124 is configuredsuch that on the side on which it protrudes laterally outward from theshift case 121, it is interlocked with an input portion of the travelingtransmission 113, and outputs drive force from the planetary powertransmission section 140 and the hydraulic continuously variabletransmission 130 to the pair of right and left travel apparatuses 101via the traveling transmission 113.

The hydraulic continuously variable transmission 130 is configured toinclude the hydraulic pump 132 whose pump shaft 132 a is rotatablysupported to the upper end side of the casing 131, and the hydraulicmotor 133 whose motor shaft 133 a is rotatably supported to the lowerend side of the casing 131. The hydraulic pump 132 is configured by avariable displacement axial plunger pump, and the hydraulic motor 133 isconfigured by a variable displacement axial plunger motor. The hydraulicmotor 133 is driven by hydraulic oil that is discharged from thehydraulic pump 132 and supplied via an oil path formed inside the portblock 134. The hydraulic continuously variable transmission 130 issupplied with replenishing hydraulic oil by a charge pump 190 mounted onthe engine-coupled side of the input shaft 122. The charge pump 190includes a rotor 190 a coupled to the input shaft 122 so as to becapable of in-unison rotation therewith, and a pump casing 190 b that isremovably coupled to the shift case 121.

Accordingly, the hydraulic continuously variable transmission 130switches between the forward power transmission state, the reverse powertransmission state, and the neutral state by an operation for changingthe angle of a swash plate 132 b that the hydraulic pump 132 is providedwith. When the hydraulic continuously variable transmission 130 isswitched to the forward power transmission state, engine drive forcetransmitted from the input shaft 122 to the pump shaft 132 a isconverted into forward drive force and output from the motor shaft 133a, and when it is switched to the reverse power transmission state,engine drive force transmitted from the input shaft 122 to the pumpshaft 132 a is converted into reverse drive force and output from themotor shaft 133 a, and thus engine drive force is subjected to steplessspeed changing and output in both the forward power transmission stateand the reverse power transmission state. When the hydrauliccontinuously variable transmission 130 is switched to the neutral state,output from the motor shaft 133 a is stopped.

The planetary power transmission section 140 is arranged so as to belocated between the motor shaft 133 a and the output rotary member 124on the same side of the hydraulic continuously variable transmission 130as the side on which the engine-coupled side of the input shaft 122 islocated. The planetary power transmission section 140 includes a sungear 142 that is supported to the power transmission shaft 123, multipleplanet gears 143 that are meshed with the sun gear 142, a ring gear 144that is meshed with the planet gears 143, and a carrier 141 thatrotatably supports the planet gears 143. The carrier 141 includes armportions 141 a that rotatably support the planet gears 143 with anextending end portion, and a tube shaft portion 141 b that is coupled tobase sides of the arm portions 141 a, and the carrier 141 is rotatablysupported to the power transmission shaft 123 with the tube shaftportion 141 b via a bearing.

The power transmission shaft 123 and the motor shaft 133 a are coupledto each other via a joint 123 a so as to be capable of in-unisonrotation, the power transmission shaft 123 and the sun gear 142 arecoupled via a spline structure so as to be capable of in-unisonrotation, and the sun gear 142 is interlocked with the motor shaft 133 aso as to be capable of in-unison rotation.

The ring gear 144 and the output rotary member 124 are interlocked so asto be capable of in-unison rotation, using an annular planet-sideinterlocking member 126 and an annular output-side interlocking member127 that are aligned axially with the power transmission shaft 123 andfit around it so as to be capable of relative rotation. Specifically,the planet-side interlocking member 126 includes multiple engaging armportions 126 a that extend radially from the outer circumferentialportion of the planet-side interlocking member 126 so as to be capableof in-unison rotation. The engaging arm portions 126 a are engaged withthe ring gear 144 at multiple locations, and the planet-sideinterlocking member 126 is interlocked with the ring gear 144 so as tobe capable of in-unison rotation. The output-side interlocking member127 is engaged with the planet-side interlocking member 126 using anengaging claw 127 a so as to be capable of in-unison rotation, isengaged with the output rotary member 124 using a spline structure so asto be capable of in-unison rotation, and is coupled to the planet-sideinterlocking member 126 and the output rotary member 124 so as to becapable of in-unison rotation. The planet-side interlocking member 126is supported to the power transmission shaft 123 via a bearing so as tobe capable of relative rotation. The output-side interlocking member 127is rotatably supported to the shift case 121 via a bearing.

The forward/reverse switching mechanism 150 includes a forward powertransmission gear 151 that is rotatably supported to the input shaft 122via a needle bearing, a forward clutch 152 that is provided so as tospan between the power transmission gear 151 and the input shaft 122, areverse power transmission shaft 153 that is rotatably supported to theshift case 121 in an arrangement parallel or substantially parallel tothe input shaft 122, a reverse rotation input gear 155 that is supportedto the reverse power transmission shaft 153 so as to be capable ofrelative rotation when meshed with a power transmission gear 154 that issupported to the input shaft 122 so as to be capable of in-unisonrotation, a reverse clutch 156 that is provided so as to span betweenthe input gear 155 and the reverse power transmission shaft 153, and areverse power transmission gear 157 that is provided so as to be capableof in-unison rotation with the reverse power transmission shaft 153.

The forward power transmission gear 151 and the reverse powertransmission gear 157 are meshed with the input gear 141 c of thecarrier 141 that is provided so as to be capable of in-unison rotationwith the tube shaft portion 141 b of the carrier 141. The input gear 155and the power transmission gear 154 are located on the side of theplanetary power transmission section 140 opposite to the side on whichthe forward power transmission gear 151 and the reverse powertransmission gear 157 are located. The forward power transmission gear151 and the reverse power transmission gear 157 are meshed with theinput gear 141 c of the planetary power transmission section 140 that islocated on the side of the sun gear 142 opposite to the side on whichthe input gear 155 and the power transmission gear 154 are located.

The forward clutch 152 is configured to include a forward clutch member152 a that is supported to the input shaft 122 so as to be capable ofin-unison rotation and sliding, and a clutch mechanism body 152 b thatis provided so as to span between one end side of the forward clutchmember 152 a and a lateral side of the forward power transmission gear151. The forward clutch member 152 a is caused to slide by a hydraulicpiston 158 fit inside an end portion of the forward clutch member 152 a.The clutch mechanism body 152 b is configured as a meshing clutch thatswitches between an on state and an off state when a meshing clawprovided on the forward clutch member 152 a and a meshing claw providedon the forward power transmission gear 151 engage/disengage with eachother.

The reverse clutch 156 is configured to include a reverse clutch member156 a that is supported to the reverse power transmission shaft 153 soas to be capable of in-unison rotation and sliding, and a clutchmechanism body 156 b that is provided so as to span between one end sideof the reverse clutch member 156 a and a lateral side of the input gear155. The reverse clutch member 156 a is caused to slide by a hydraulicpiston 159 fit inside an end portion of the reverse clutch member 156 a.The clutch mechanism body 156 b is configured as a meshing clutch thatswitches between an on state and an off state when a meshing clawprovided on the reverse clutch member 156 a and a meshing claw providedon the input gear 155 engage/disengage with each other.

When the forward clutch 152 is switched to the on state, and the reverseclutch 156 is switched to the off state, the forward/reverse switchingmechanism 150 enters the forward power transmission state, inputs driveforce of the input shaft 122 from the forward clutch member 152 a thatis located between the engine-coupled side and the hydrauliccontinuously variable transmission-coupled side of the input shaft 122,converts the drive force from the input shaft 122 into forward driveforce, and transmits it from the forward power transmission gear 151 tothe carrier 141 of the planetary power transmission section 140.

When the forward clutch 152 is switched to the off state, and thereverse clutch 156 is switched to the on state, the forward/reverseswitching mechanism 150 enters the reverse power transmission state,inputs drive force of the input shaft 122 from the power transmissiongear 154 that is located between the engine-coupled side and thehydraulic continuously variable transmission-coupled side of the inputshaft 122, converts the drive force from the input shaft 122 intoreverse drive force, and transmits it from the reverse powertransmission gear 157 to the carrier 141 of the planetary powertransmission section 140.

When the forward clutch 152 and the reverse clutch 156 are switched tothe off state, the forward/reverse switching mechanism 150 enters theneutral state and cuts off the interlocking of the input shaft 122 andthe carrier 141 of the planetary power transmission section 140.

An output-side clutch mechanism 160 that includes a clutch member 161fit around the power transmission shaft 123 is provided so as to spanbetween the sun gear 142 of the planetary power transmission section 140and the planet-side interlocking member 126.

When hydraulic oil is supplied to an oil chamber formed on the innercircumferential side of the clutch member 161, the clutch member 161switches to an off position by being caused to slide toward the sun gear142 in resistance to an on biasing spring 162, and when hydraulic oil isdischarged from the oil chamber, the clutch member 161 switches to an onposition by being caused to slide toward the planet-side interlockingmember 126 by the on biasing spring 162. When the clutch member 161switches to the on position, a clutch claw 161 a provided on the clutchmember 161 engages with a clutch claw provided on the planet-sideinterlocking member 126, and thus the clutch member 161 is coupled tothe planet-side interlocking member 126 so as to be capable of in-unisonrotation. The clutch member 161 is caused to slide while maintaining thestate of being engaged with the sun gear 142 so as to be capable ofin-unison rotation by the engaging claw 161 b, and reaches the onposition while maintaining the engaged state with respect to the sungear 142. When the clutch member 161 switches to the off position, theengagement with the planet-side interlocking member 126 using the clutchclaw 161 a is canceled.

Accordingly, with the output-side clutch mechanism 160, when the clutchmember 161 is switched to the off position, the interlocking between thesun gear 142 and the planet-side interlocking member 126 is cut off,thus cutting off the interlocking of the motor shaft 133 a to the outputrotary member 124, and this achieves a first power transmission state inwhich the ring gear 144 of the planetary power transmission section 140and the output rotary member 124 are interlocked so as to be capable ofin-unison rotation, thus enabling combined drive force from theplanetary power transmission section 140 to be output from the outputrotary member 124.

With the output-side clutch mechanism 160, when the clutch member 161 isswitched to the on position, the sun gear 142 and the planet-sideinterlocking member 126 are interlocked so as to be capable of in-unisonrotation, and this achieves a second power transmission state in whichthe motor shaft 133 a is interlocked with the output rotary member 124so as to be capable of in-unison rotation, thus enabling output from thehydraulic continuously variable shift apparatus 130 to be output fromthe output rotary member 124. Also, when the sun gear 142 and the powertransmission shaft 123 are interlocked so as to be capable of in-unisonrotation, and the ring gear 144 and the planet-side interlocking member126 are interlocked so as to be capable of in-unison rotation, the sungear 142, the planet gears 143, and the ring gear 144 can rotate inunison with the motor shaft 133 a such that autorotation of the planetgears 143 does not occur.

Accordingly, with the planetary power transmission section 140, when theforward/reverse switching mechanism 150 is switched to the forward powertransmission state, and the output-side clutch mechanism 160 is switchedto the off state, forward drive force from the input shaft 122 isinputted to the carrier 141 via the forward/reverse switching mechanism150, output from the motor shaft 133 a of the hydraulic continuouslyvariable shift apparatus 130 is inputted to the sun gear 142 via thepower transmission shaft 123, forward drive force from the input shaft122 and output from the hydraulic continuously variable shift apparatus130 are combined to generate forward-side combined drive force, and thegenerated forward-side combined drive force is outputted from the ringgear 144 to the output rotary member 124 via the planet-sideinterlocking member 126 and the output-side interlocking member 127.

With the planetary power transmission section 140, when theforward/reverse switching mechanism 150 is switched to the reverse powertransmission state, and the output-side clutch mechanism 160 is switchedto the off state, reverse drive force from the input shaft 122 isinputted to the carrier 141 via the forward/reverse switching mechanism150, output from the motor shaft 133 a of the hydraulic continuouslyvariable shift apparatus 130 is inputted to the sun gear 142 via thepower transmission shaft 123, forward drive force from the input shaft122 and output from the hydraulic continuously variable shift apparatus130 are combined to generate reverse-side combined drive force, and thegenerated reverse-side combined drive force is outputted from the ringgear 144 to the output rotary member 124 via the planet-sideinterlocking member 126 and the output-side interlocking member 127.

When the forward/reverse switching mechanism 150 is switched to theneutral state, the planetary power transmission section 140 enters astate in which interlocking with the input shaft 122 is cut off.

FIG. 22 is an illustrative diagram showing the relationship that theoperation states of the hydraulic continuously variable transmission130, the forward clutch 152, the reverse clutch 156, and the output-sideclutch mechanism 160 have with the power transmission mode of the shiftpower transmission apparatus 120. In FIG. 22, “forward” indicates theforward power transmission state of the hydraulic continuously variabletransmission 130, and “reverse” indicates the reverse power transmissionstate of the hydraulic continuously variable transmission 130. In FIG.22, “OFF” indicates the off state of the forward clutch 152, the reverseclutch 156, and the output-side clutch mechanism 160, and “ON” indicatesthe on state of the forward clutch 152, the reverse clutch 156, and theoutput-side clutch mechanism 160. FIG. 19 is a front view in verticalsection of the shift power transmission apparatus 120 in the state inwhich HST mode power transmission is achieved.

FIG. 19 is a front view in vertical section of the shift powertransmission apparatus 120 during HST mode power transmission. A shownin FIGS. 19 and 22, when the forward clutch 152 and the reverse clutch156 are controlled so as to be switched to the off state, and theoutput-side clutch mechanism 160 is controlled so as to be switched tothe on state, the shift power transmission apparatus 120 enters thestate in which HST mode power transmission is achieved. When the shiftpower transmission apparatus 120 enters the HST mode power transmissionstate, engine drive force input by the input shaft 122 is subjected tospeed change by only the hydraulic continuously variable transmission130 without being transmitted to the planetary power transmissionsection 140, the speed-changed drive force is transmitted from the motorshaft 133 a to the output rotary member 124 via the power transmissionshaft 123, the sun gear 142, the clutch member 161, the planet-sideinterlocking member 126, and the output-side interlocking member 127,and then transmitted from the output rotary member 124 to the pair ofright and left travel apparatuses 101.

FIG. 20 is a front view in vertical section of the shift powertransmission apparatus 120 during forward-side HMT mode powertransmission. As shown in FIGS. 20 and 22, when the forward clutch 152is controlled so as to switch to the on state, and the reverse clutch156 and the output-side clutch mechanism 160 are controlled so as toswitch to the off state, the shift power transmission apparatus 120enters a state in which forward-side HMT mode power transmission isachieved. When the shift power transmission apparatus 120 enters theforward-side HMT mode power transmission state, engine drive force inputby the input shaft 122 is converted into forward drive force by theforward/reverse switching mechanism 150 and transmitted to the planetarypower transmission section 140, the planetary power transmission section140 combines the forward drive force from the forward/reverse switchingmechanism 150 with output from the motor shaft 133 a of the hydrauliccontinuously variable transmission 130 so as to generate forward-sidecombined drive force, and the generated forward-side combined driveforce is transmitted from the ring gear 144 to the output rotary member124 via the planet-side interlocking member 126 and the output-sideinterlocking member 127, and then transmitted from the output rotarymember 124 to the pair of right and left travel apparatuses 101.

FIG. 21 is a front view in vertical section of the shift powertransmission apparatus 120 during reverse-side HMT mode powertransmission. As shown in FIGS. 21 and 22, when the reverse clutch 156is controlled so as to switch to the on state, and the forward clutch152 and the output-side clutch mechanism 160 are controlled so as toswitch to the off state, the shift power transmission apparatus 120enters a state in which reverse-side HMT mode power transmission isachieved. When the shift power transmission apparatus 120 enters thereverse-side HMT mode power transmission state, engine drive force inputby the input shaft 122 is converted into reverse drive force by theforward/reverse switching mechanism 150 and transmitted to the planetarypower transmission section 140, the planetary power transmission section140 combines the reverse drive force from the forward/reverse switchingmechanism 150 with output from the motor shaft 133 a of the hydrauliccontinuously variable transmission 130 so as to generate reverse-sidecombined drive force, and the generated reverse-side combined driveforce is transmitted from the ring gear 144 to the output rotary member124 via the planet-side interlocking member 126 and the output-sideinterlocking member 127, and then transmitted from the output rotarymember 124 to the pair of right and left travel apparatuses 101.

FIG. 23 is an illustrative diagram showing the relationship between theshift state of the hydraulic continuously variable transmission 130 andthe output speed of the output rotary member 124 of the shift powertransmission apparatus 120 in the state in which the accelerator of theengine 108 is set such that a set constant speed of drive force isoutput. In FIG. 23, the horizontal axis indicates the shift state of thehydraulic continuously variable transmission 130, “n” indicates theneutral position of the hydraulic continuously variable transmission130, “−max” indicates the maximum speed position in the reverse powertransmission state of the hydraulic continuously variable transmission130, and “+max” indicates the maximum speed position in the forwardpower transmission state of the hydraulic continuously variabletransmission 130. The vertical axis in FIG. 23 indicates the outputspeed of the output rotary member 124. A solid line RL and a solid lineFL shown in FIG. 23 indicate change in the output speed when the forwardclutch 152 and the reverse clutch 156 are controlled so as to switch tothe off state, and the output-side clutch mechanism 160 is controlled soas to switch to the on state, that is to say, when the shift powertransmission apparatus 120 is put in the HST mode power transmissionstate. Solid lines FM and FH shown in FIG. 23 indicate change in theoutput speed when the forward clutch 152 is controlled so as to switchto the on state, and the reverse clutch 156 and the output-side clutchmechanism 160 are controlled so as to switch to the off state, that isto say, when the shift power transmission apparatus 120 is put in theforward-side HMT mode power transmission state. Solid lines RM and RHshown in FIG. 23 indicate change in the output speed when the reverseclutch 156 is controlled so as to switch to the on state, and theforward clutch 152 and the output-side clutch mechanism 160 arecontrolled so as to switch to the off state, that is to say, when theshift power transmission apparatus 120 is put in the reverse-side HMTmode power transmission state.

As shown in FIG. 22, and as shown by the solid line FL in FIG. 23, inthe state in which the forward clutch 152 and the reverse clutch 156 arein the off state, and the output-side clutch mechanism 160 is in the onstate, if the hydraulic continuously variable transmission 130 isoperated to the neutral position “n”, the output changes to zero “0”.

While the forward clutch 152 and the reverse clutch 156 are maintainedin the off state, and the output-side clutch mechanism 160 is maintainedin the on state, if the hydraulic continuously variable transmission 130is shifted from the neutral position “n” toward the maximum speedposition “+max” in the forward power transmission state, forward driveforce is output. While the forward clutch 152 and the reverse clutch 156are maintained in the off state, and the output-side clutch mechanism160 is maintained in the on state, as the hydraulic continuouslyvariable transmission 130 is shifted from the neutral position “n”toward the maximum speed position “+max” in the forward powertransmission state, forward output steplessly increases. When thehydraulic continuously variable transmission 130 reaches the maximumspeed position “+max” in the forward power transmission state, theoutput speed reaches a forward intermediate speed “FV1”.

As shown in FIG. 22, and as shown by the solid lines FM and FH in FIG.23, when the hydraulic continuously variable transmission 130 reachesthe maximum speed position “+max” in the forward power transmissionstate, the forward clutch 152 is controlled so as to switch to the onstate, and the output-side clutch mechanism 160 is controlled so as toswitch to the off state, and, while the forward clutch 152 is maintainedin the on state, and the reverse clutch 156 and the output-side clutchmechanism 160 are maintained in the off state, as the hydrauliccontinuously variable shift apparatus 130 is shifted from the maximumspeed position “+max” in the forward power transmission state toward themaximum speed position “−max” in the reverse power transmission state,the forward output steplessly increases from the intermediate speed“FV1”. When the hydraulic continuously variable transmission 130 reachesthe maximum speed position “−max” in the reverse power transmissionstate, the output speed reaches a forward intermediate speed “FV2”.

As shown in FIG. 22, and as shown by the solid line RL in FIG. 23, whilethe forward clutch 152 and the reverse clutch 156 are maintained in theoff state, and the output-side clutch mechanism 160 is maintained in theon state, if the hydraulic continuously variable transmission 130 isshifted from the neutral position “n” toward to the maximum speedposition “−max” in the reverse power transmission state, reverse driveforce is output. While the forward clutch 152 and the reverse clutch 156are maintained in the off state, and the output-side clutch mechanism160 is maintained in the on state, as the hydraulic continuouslyvariable transmission 130 is shifted from the neutral position “n”toward the maximum speed position “−max” in the reverse powertransmission state, reverse output steplessly increases. When thehydraulic continuously variable transmission 130 reaches the maximumspeed position “−max” in the reverse power transmission state, theoutput speed reaches a reverse intermediate speed “RV1”.

As shown in FIG. 22, and as shown by the solid lines RM and RH in FIG.23, when the hydraulic continuously variable transmission 130 reachesthe maximum speed position “−max” in the reverse power transmissionstate, the reverse clutch 156 is controlled so as to switch to the onstate, and the output-side clutch mechanism 160 is controlled so as toswitch to the off state, and, while the reverse clutch 156 is maintainedin the on state, and the forward clutch 152 and the output-side clutchmechanism 160 are maintained in the off state, as the hydrauliccontinuously variable shift apparatus 130 is shifted from the maximumspeed position “−max” in the reverse power transmission state toward themaximum speed position “+max” in the forward power transmission state,the reverse output steplessly increases from the intermediate speed“RV1”. When the hydraulic continuously variable transmission 130 reachesthe maximum speed position “+max” in the forward power transmissionstate, the output reaches a reverse intermediate speed “RV2”.

In FIG. 23, “N” indicates the value on the horizontal axis when thesolid lines FH and FM extend beyond the forward-side maximum speedposition “+max” of the hydraulic continuously variable transmission 130to the point at which the output rotation reaches zero “0”. Letting 1 bethe horizontal axis value for the forward-side maximum speed position“+max” of the hydraulic continuously variable transmission 130, N=1.6 to2.2. In other words, the capacities of the hydraulic pump 132 and thehydraulic motor 133 in the hydraulic continuously variable transmission130 and the power transmission gear ratio of the planetary powertransmission section 140 are set such that N=1.6 to 2.2.

FIG. 24 is a block diagram showing a shift operation apparatus 171 thatperforms shift operations on the shift power transmission apparatus 120.As shown in this figure, the shift operation apparatus 171 includes acontrol apparatus 172 that is linked to the shift operation section 130a of the hydraulic continuously variable transmission 130 and operationsections 152 c, 156 c, and 160 a of the forward clutch 152, the reverseclutch 156, and the output-side clutch mechanism 160, as well as theshift detection sensor 173, the engine speed sensor 174, thetransmission output speed sensor 175, and the output speed sensor 176that are linked to the control apparatus 172.

The shift operation section 130 a is configured by an electricalactuator or a hydraulic actuator that operates so as to change the angleof the swash plate 132 b of the hydraulic pump 132 in the hydrauliccontinuously variable shift apparatus 130. The operation section 152 cof the forward clutch 152 is configured by an operation valve that isconnected to a hydraulic piston 158 via an operation oil path formedinside the input shaft 122, and by operating the hydraulic piston 158 soas to cause the forward clutch member 152 a to slide, the operationsection 152 c switches the forward clutch 152. The operation section 156c of the reverse clutch 156 is configured by an operation valve that isconnected to a hydraulic piston 159 via an operation oil path formedinside the reverse power transmission shaft 153, and by operating thehydraulic piston 159 so as to cause the reverse clutch member 156 a toslide, the operation section 156 c switches the reverse clutch 156. Theoperation section 160 c of the output-side clutch mechanism 160 isconfigured by an operation valve that is connected to the oil chamber ofthe clutch member 161 via an operation oil path formed inside the powertransmission shaft 123, and by supplying/discharging operation oilto/from the oil chamber of the clutch member 161, the operation sectiont160 c causes the clutch member 161 to slide so as to switch theoutput-side clutch mechanism 160.

The shift detection sensor 173 detects the operation position of a shiftlever 177, and outputs this detection result to the control apparatus172. The engine speed sensor 174 detects the rotational speed of theengine 108, and outputs this detection result to the control apparatus172. The transmission output speed sensor 175 detects the output speedof the hydraulic continuously variable transmission 130, and outputsthis detection result to the control apparatus 172. The output speedsensor 176 detects the output speed of the shift power transmissionapparatus 120, and outputs this detection result to the controlapparatus 172.

The control apparatus 172 is configured using a microcomputer, andincludes a shift control module 178. Based on the detection informationfrom the shift detection sensor 173 and the transmission output speedsensor 175, the shift control module 178 performs shift control on thehydraulic continuously variable transmission by operating the shiftoperation section 130 a such that the shift state of the hydrauliccontinuously variable transmission 130 corresponds to the operationposition of the shift lever 177.

In addition to performing shift control on the hydraulic continuouslyvariable transmission 130, the shift control module 178 detects therotational speed of the engine 108, whose accelerator has been set,based on the detection information from the engine speed sensor 174, andthen, based on this detection result and the detection information fromthe shift detection sensor 173, the transmission output speed sensor175, and the output speed sensor 176, the shift control module 178performs control for operating the operation section 152 c, theoperation section 156 c, and the operation section 160 c so as to switchthe forward clutch 152, the reverse clutch 156, and the output-sideclutch mechanism 160 in accordance with predetermined timing so that theshift power transmission apparatus 120 transmits power while achievingHST mode power transmission, forward-side HMT mode power transmission,and reverse-side HMT mode power transmission as shown in FIGS. 22 and23.

Alternative Embodiment

FIG. 25 is a front view in vertical section of the shift powertransmission apparatus 120 having an alternative embodiment structure.As shown in this figure, in the shift power transmission apparatus 120having the alternative embodiment structure, the charge pump 190 thatsupplies replenishing hydraulic oil to the hydraulic continuouslyvariable transmission 130 is mounted to an end portion of the pump shaft132 a. The charge pump 190 includes a rotor 190 a attached to the pumpshaft 132 a so as to be capable of in-unison rotation therewith, and apump casing 190 b that is removably coupled to the casing 131.

Other Alternative Embodiments

(1) Although the above-described embodiment gives the example where theforward/reverse switching mechanism 150 is configured such that theratio of power transmission from the input shaft 122 to the carrier 141in the forward power transmission state and the ratio of powertransmission from the input shaft 122 to the carrier 141 in the reversepower transmission state are the same or substantially the same, it ispossible to employ a forward/reverse switching mechanism configured suchthat the ratio of power transmission from the input shaft 122 to thecarrier 141 in the forward power transmission state and the ratio ofpower transmission from the input shaft 122 to the carrier 141 in thereverse power transmission state are different. In this case, the angleof inclination of the solid lines RM and RH indicating the output speedin reverse-side HMT mode power transmission relative to the horizontalaxis and the angle of inclination of the solid lines FM and FHindicating the output speed in forward-side HMT mode power transmissionmay be the same or different, and the maximum speed of reverse outputand the maximum speed of forward output may be the same or different.

(2) Although the above-described embodiment gives the example where thereverse clutch 156 is provided so as to span between the input gear 155and the reverse power transmission shaft 153, an implementation ispossible in which the input gear 155 is supported to the reverse powertransmission shaft 153 so as to be capable of in-unison rotation, thereverse power transmission gear 157 is supported to the reverse powertransmission shaft 153 so as to be capable of relative rotation, and thereverse clutch 156 is provided so as to span between the reverse powertransmission gear 157 and the reverse power transmission shaft 153.

(3) Although the above-described embodiment gives the example where theforward clutch 152, the reverse clutch 156, and the output-side clutchmechanism 160 are configured by a meshing type of clutch, animplementation is possible in which they are configured by a frictiontype of clutch.

(4) Although the above-described embodiment gives the example whereforward drive force and reverse drive force from the forward/reverseswitching mechanism 150 is inputted to the carrier 141 of the planetarypower transmission section 140, and drive force from the ring gear 144of the planetary power transmission section 140 is transmitted to theoutput rotary member 124, a configuration may be implemented in whichforward drive force and reverse drive force from the forward/reverseswitching mechanism 150 is inputted to the ring gear 144 of theplanetary power transmission section 140, and drive force from thecarrier 141 of the planetary power transmission section 140 istransmitted to the output rotary member 124.

(5) Although the above-described embodiment gives the example where thehydraulic motor 133 has a variable displacement configuration, animplementation is possible in which it has a fixed capacityconfiguration.

Third Embodiment

Next, a third embodiment will be described with reference to FIGS. 28 to44.

As shown in FIG. 28, the combine, which performs the task of harvestingrice, barley, and the like, is configured to be self-propelled with apair of right and left crawling travel apparatuses 201, and isconfigured to include a traveling body equipped with a riding drivingsection 202, a reaping section 204 coupled to the front portion of abody frame 203 of the traveling body, a threshing apparatus 205 providedso as to be arranged rearward of the reaping section 204 on the rearside of the body frame 203, and a grain tank 206 provided so as to bearranged to the side of the threshing apparatus 205 on the rear side ofthe body frame 203.

Specifically, the reaping section 204 includes a reaping section frame204 a that extends forward from the front portion of the body frame 203in a vertically swingable manner, and when the reaping section frame 204a is swung by an elevating cylinder 207, the reaping section 204 movesup/down between a lowered operating position at which a divider 204 b,which is provided at the front edge portion of the reaping section 204,is lowered close to the ground, and a raised non-operating position atwhich the divider 204 b is raised high above the ground. When thetraveling body is caused to travel with the reaping section 204 loweredto the lowered operating position, the reaping section 204 operates suchthat reaping-target planted stalks are guided to a raising path by thedivider 204 b, the planted stalks that were guided to the raising pathare reaped by a clipper-type reaping apparatus 204 d while being raisedup by a raising apparatus 204 c, and the reaped stalks are supplied tothe threshing apparatus 205 by a supplying apparatus 204 e. In thethreshing apparatus 205, the reaped stalks are conveyed from thesupplying apparatus 204 e toward the rear of the apparatus body withtheir base sides clamped by a threshing feed chain 205 a, the eartip-sides of the reaped stalks are supplied to a handling compartment(not shown) where they are subjected to reaping processing, and thereaped grain is fed to the grain tank 206.

The combine is configured such that an engine 208 is provided underneatha driver seat 202 a provided in the driving section 202, and drive forceoutputted by the engine 208 is transmitted to the pair of right and lefttravel apparatuses 201 by a travel power transmission apparatus 210 thatincludes a transmission case 211 provided at the front edge portion ofthe body frame 203.

FIG. 29 is a front view of the schematic structure of the travel powertransmission apparatus 210. As shown in this figure, in the travel powertransmission apparatus 210, engine drive force from an output shaft 208a of the engine 208 is inputted to a shift power transmission device 220provided on the side of the upper end portion of the transmission case211 via a power train 212 provided with a power transmission belt 212 a.Output of the shift power transmission device 220 is inputted to atraveling transmission 213 provided inside the transmission case 211,then transmitted from a left-side steering clutch mechanism 214, whichis one of a pair of right and left steering clutch mechanisms 214included in the traveling transmission 213, to a drive shaft 201 a ofthe left-side travel apparatus 201, and also transmitted from theright-side steering clutch mechanism 214 to a drive shaft 201 a of theright-side travel apparatus 201.

The travel power transmission apparatus 210 includes a reapingtransmission 215 that is provided inside the transmission case 211, andoutput of the shift power transmission device 220 is inputted to thereaping transmission 215 and transmitted from a reaping output shaft 216to a drive shaft 204 f of the reaping section 204.

Next, the shift power transmission device 220 will be described.

As shown in FIGS. 30 and 31, the shift power transmission device 220 isconfigured to include a planetary shift section 220A, which is providedwith a shift case 221 whose side portion is coupled to the upper endside of the transmission case 211, and a hydrostatic continuouslyvariable shift section 230 that has a casing 231 coupled to the sideportion on the side opposite to the side on which the shift case 221 iscoupled to the transmission case 211.

The shift case 221 is configured to include a main case portion 221 athat accommodates a planetary power transmission section 240 and a powertrain 250, and a coupling case portion 221 b that accommodates aconnection portion between the continuously variable shift section 230and an input shaft 222 and a power transmission shaft 223, and thatcouples the shift case 221 with a port block 234 of the casing 231. Theshift case 221 is coupled to the transmission case 211 with a bulgingportion 221 c formed so as to bulge outward horizontally on the sideface of the lower portion of the main case portion 221 a where theoutput rotary member 224 is located. The size of the coupling caseportion 221 b in the up/down direction of the traveling body is smallerthan the size of the main case portion 221 a in the up/down direction ofthe traveling body. The main case portion 221 a is formed such that theshape in vertical section is vertically elongated when viewed in thefront/rear direction of the apparatus body, the casing 231 is formedsuch that the shape in vertical section is vertically elongated whenviewed in the front/rear direction of the apparatus body, the planetaryshift section 220A and the continuously variable shift section 230 arealigned in the horizontal direction of the apparatus body such that theshift power transmission device 220 has a small width overall in thehorizontal direction of the apparatus body, and the shift powertransmission device 220 is coupled to the lateral side of thetransmission case 211 in a compact state with respect to the left/rightdirection of the traveling body so as to not protrude outwardhorizontally. Furthermore, the side face of the lower portion of thecasing 231 is formed so as to have an inclined face 231A that isinclined toward the interior of the apparatus in the downward direction.A bulging portion 231B that supports a bearing of a motor shaft 233 a isformed on the inclined face 231A, thus making the shift powertransmission device 220 even more compact. Also, an oil filter 220F isarranged facing upward on the upper face of the casing 231, and furthercompactness is achieved by preventing the oil filter 220F fromprotruding outward horizontally.

The planetary shift section 220A includes the input shaft 222 that isoriented in the horizontal direction of the apparatus body and isrotatably supported to the upper end side of the shift case 221, a powertransmission shaft 223 and a rotating shaft-type of output rotary member224 that are rotatably supported to the lower end side of the shift case221 parallel or substantially parallel to the input shaft 222, theplanetary power transmission section 240 that is supported to the powertransmission shaft 223, and the power train 250 provided so as to spanfrom the input shaft 222 to a carrier 241 of the planetary powertransmission section 240.

The input shaft 222 is arranged so as to be coaxially aligned with apump shaft 232 a of the continuously variable shift section 230. Theinput shaft 222 is configured such that on the side on which itprotrudes laterally outward from the shift case 221, it is coupled withan output shaft 208 a of the engine 208 via the power train 212, and onthe side opposite to the side coupled to the engine 208, it is coupledto the pump shaft 232 a of the continuously variable shift section 230so as to be capable of in-unison rotation therewith via a joint 222 a.The input shaft 222 receives engine drive force via the power train 212,and drives the hydraulic pump 232 of the continuously variable shiftsection 230 upon being driven by engine drive force.

The output rotary member 224 is arranged so as to be coaxially alignedwith a motor shaft 233 a of the continuously variable shift section 230on the same side of the continuously variable shift section 230 as theside on which the engine-coupled side of the input shaft 222 is located.The output rotary member 224 is configured such that on the side onwhich it protrudes laterally outward from the shift case 221, it isinterlocked with an input portion of the traveling transmission 213, andoutputs drive force from the planetary power transmission section 240and the continuously variable shift section 230 to the pair of right andleft travel apparatuses 201 via the traveling transmission 213.

The continuously variable shift section 230 is configured to include thehydraulic pump 232 whose pump shaft 232 a is rotatably supported to theupper end side of the casing 231, and the hydraulic motor 233 whosemotor shaft 233 a is rotatably supported to the lower end side of thecasing 231. The hydraulic pump 232 is configured by a variabledisplacement axial plunger pump, and the hydraulic motor 233 isconfigured by an axial plunger motor. The hydraulic motor 233 is drivenby hydraulic oil that is discharged from the hydraulic pump 232 andsupplied via an oil path formed inside the port block 234. Thecontinuously variable shift section 230 is supplied with replenishinghydraulic oil by a charge pump 290 mounted to an end portion of the pumpshaft 232 a. The charge pump 290 includes a rotor 290 a attached to thepump shaft 232 a so as to be capable of in-unison rotation therewith,and a pump casing 290 b that is removably coupled to the casing 231.

Accordingly, the continuously variable shift section 230 switchesbetween the forward power transmission state, the reverse powertransmission state, and the neutral state by an operation for changingthe angle of a swash plate 232 b that the hydraulic pump 232 is providedwith. When the continuously variable shift section 230 is switched tothe forward power transmission state, engine drive force transmittedfrom the input shaft 222 to the pump shaft 232 a is converted intoforward drive force and output from the motor shaft 233 a, and when itis switched to the reverse power transmission state, engine drive forcetransmitted from the input shaft 222 to the pump shaft 232 a isconverted into reverse drive force and output from the motor shaft 233a, and thus engine drive force is subjected to stepless speed changingand output in both the forward power transmission state and the reversepower transmission state. When the hydraulic continuously variable shiftsection 230 is switched to the neutral state, output from the motorshaft 233 a is stopped.

The planetary power transmission section 240 is arranged so as to belocated between the motor shaft 233 a and the output rotary member 224on the same side of the continuously variable shift section 230 as theside on which the engine-coupled side of the input shaft 222 is located.The planetary power transmission section 240 includes a sun gear 242that is supported to the power transmission shaft 223, multiple planetgears 243 that are meshed with the sun gear 242, a ring gear 244 that ismeshed with the planet gears 243, and a carrier 241 that rotatablysupports the planet gears 243. The carrier 241 includes arm portions 241a that rotatably support the planet gears 243 with an extending endportion, and a tube shaft portion 241 b that is coupled to base sides ofthe arm portions 241 a, and the carrier 241 is rotatably supported tothe power transmission shaft 223 with the tube shaft portion 241 b via abearing.

The power transmission shaft 223 and the motor shaft 233 a are coupledto each other via a joint 223 a so as to be capable of in-unisonrotation, the power transmission shaft 223 and the sun gear 242 arecoupled via a spline structure so as to be capable of in-unisonrotation, and the sun gear 242 is interlocked with the motor shaft 233 aso as to be capable of in-unison rotation.

The ring gear 244 and the output rotary member 224 are interlocked so asto be capable of in-unison rotation, using an annular planet-sideinterlocking member 226 and an annular output-side interlocking member227 that are aligned axially with the power transmission shaft 223 andfit around it so as to be capable of relative rotation. Specifically,the planet-side interlocking member 226 includes multiple engaging armportions 226 a that extend radially from the outer circumferentialportion of the planet-side interlocking member 226 so as to be capableof in-unison rotation. The engaging arm portions 226 a are engaged withthe ring gear 244 at multiple locations, and the planet-sideinterlocking member 226 is interlocked with the ring gear 244 so as tobe capable of in-unison rotation. The output-side interlocking member227 is engaged with the planet-side interlocking member 226 using anengaging claw 227 a so as to be capable of in-unison rotation, isengaged with the output rotary member 224 using a spline structure so asto be capable of in-unison rotation, and is coupled to the planet-sideinterlocking member 226 and the output rotary member 224 so as to becapable of in-unison rotation. The planet-side interlocking member 226is supported to the power transmission shaft 223 via a bearing so as tobe capable of relative rotation. The output-side interlocking member 227is rotatably supported to the shift case 221 via a bearing.

The power train 250 is configured to include a power transmission gear252 that is supported to the input shaft 222 via a needle bearing so asto be capable of relative rotation in a state of being meshed with aninput gear 241 c of the carrier 241 that is provided so as to be capableof in-unison rotation with the tube shaft portion 241 b of the carrier241, and an HMT clutch 255 provided so as to span between the powertransmission gear 252 and the input shaft 222.

The HMT clutch 255 is configured to include a clutch member 256supported to the input shaft 222 so as to be capable of in-unisonrotation and sliding, and a clutch body 257 provided so as to spanbetween one end side of the clutch member 256 and a lateral side of thepower transmission gear 252. The clutch member 256 is caused to slide bya hydraulic piston 258 that is fit inside an end portion of the clutchmember 256. The clutch body 257 is configured as a meshing clutch thatswitches between an on state and an off state when a meshing clawprovided on the clutch member 256 and a meshing claw provided on thepower transmission gear 252 engage/disengage with each other.

When the clutch body 257 is switched to the on state, the HMT clutch 255is switched to the on state such that the input shaft 222 and the powertransmission gear 252 are interlocked so as to be capable of in-unisonrotation, and thus the HMT clutch 255 enters the state in which HMTpower transmission is set so that the carrier 241 of the planetary powertransmission section 240 and the input shaft 222 are interlocked.

When the clutch body 257 is switched to the off state, the HMT clutch255 is switched to the off state such that the interlocking of the inputshaft 222 and the power transmission gear 252 is cut off, and thus theHMT clutch 255 enters the state in which the HMT power transmissionsetting is canceled so that the interlocking of the carrier 241 of theplanetary power transmission section 240 and the input shaft 222 is cutoff.

Accordingly, in the planetary power transmission section 240, when the

HMT clutch 255 is switched to the state in which HMT power transmissionis set, drive force from the input shaft 222 is inputted from a sitelocated between the engine-coupled side and the continuously variableshift section-coupled side of the input shaft 222 to the carrier 241 viathe power train 250. When the HMT clutch 255 is switched to the state inwhich the HMT power transmission setting is canceled, the planetarypower transmission section 240 enters a state in which interlocking ofthe carrier 241 with the input shaft 222 is cut off.

An HST clutch 260 that includes a clutch member 261 fit around the powertransmission shaft 223 is provided so as to span between the sun gear242 of the planetary power transmission section 240 and the planet-sideinterlocking member 226.

When hydraulic oil is supplied to an oil chamber formed on the innercircumferential side of the clutch member 261, the clutch member 261switches to an off position by being caused to slide toward the sun gear242 in resistance to an on biasing spring 262, and when hydraulic oil isdischarged from the oil chamber, the clutch member 261 switches to an onposition by being caused to slide toward the planet-side interlockingmember 226 by the on biasing spring 262. When the clutch member 261switches to the on position, a clutch claw 261 a provided on the clutchmember 261 engages with a clutch claw provided on the planet-sideinterlocking member 226, and thus the clutch member 261 is coupled tothe planet-side interlocking member 226 so as to be capable of in-unisonrotation. The clutch member 261 is caused to slide while maintaining thestate of being engaged with the sun gear 242 so as to be capable ofin-unison rotation by the engaging claw 261 b, and reaches the onposition while maintaining the engaged state with respect to the sungear 242. When the clutch member 261 switches to the off position, theengagement with the planet-side interlocking member 226 using the clutchclaw 261 a is canceled.

Accordingly, with the HST clutch 260, when the clutch member 261 isswitched to the on position, the sun gear 242 and the planet-sideinterlocking member 226 are interlocked so as to be capable of in-unisonrotation, and this achieves a state in which HST power transmission isset so that the motor shaft 233 a is interlocked with the output rotarymember 224 so as to be capable of in-unison rotation, thus enablingoutput from the continuously variable shift section 230 to be outputfrom the output rotary member 224. Also, when HST power transmission isset in the HST clutch 260, when the sun gear 242 and the powertransmission shaft 223 are interlocked so as to be capable of in-unisonrotation, and the ring gear 244 and the planet-side interlocking member226 are interlocked so as to be capable of in-unison rotation, the sungear 242, the carrier 241, and the ring gear 244 can rotate in unisonwith the motor shaft 233 a such that autorotation of the planet gears243 does not occur.

The HST clutch 260 switches the sun gear 242 of the planetary powertransmission section 240 and the output rotary member 224 between theinterlocking-on state and the interlocking-off state while maintainingthe interlocked state between the ring gear 244 of the planetary powertransmission section 240 and the output rotary member 224.

When the clutch member 261 is switched to the off position, the HSTclutch 260 enters the state in which the setting of HST powertransmission is canceled so that the interlocking of the sun gear 242and the planet-side interlocking member 226 is cut off, the interlockingof the motor shaft 233 a with the output rotary member 224 is cut off,and a state is realized in which the ring gear 244 of the planetarypower transmission section 240 and the output rotary member 224 areinterlocked so as to be capable of in-unison rotation, thus enablingcombined drive force from the planetary power transmission section 240to be output from the output rotary member 224.

Accordingly, with the planetary power transmission section 240, when theHMT clutch 255 is switched to the state in which HST power transmissionis set, and the HST clutch 260 is switched to the state in which thesetting of HST power transmission is canceled, drive force transmittedfrom the engine to the input shaft 222 is inputted to the carrier 241via the power train 250, speed-changed drive force output from the motorshaft 233 a of the continuously variable shift section 230 is inputtedto the sun gear 242 via the power transmission shaft 223, drive forcefrom the engine and speed-changed drive force output from motor shaft233 a of the continuously variable shift section 230 are combined togenerate combined drive force, and the generated combined drive force isoutputted from the ring gear 244 to the output rotary member 224 via theplanet-side interlocking member 226 and the output-side interlockingmember 227.

In other words, the clutch mechanism 270 is configured to include theHMT clutch 255 and the HST clutch 260 in order to perform powertransmission setting for switching the setting of the shift powertransmission device 220 between HMT power transmission and HST powertransmission.

FIG. 32 is an illustrative diagram showing the relationship that theoperation states of the HMT clutch 255 and the HST clutch 260, theoperation state of the power transmission setting clutch mechanism 270,and the power transmission mode of the shift power transmission device220 have with each other. In FIG. 32, “OFF” indicates the off state ofthe HMT clutch 255 and the HST clutch 260, and “ON” indicates the onstate of the HMT clutch 255 and the HST clutch 260. As shown in thisfigure, when the HMT clutch 255 is switched to the off state and the HSTclutch 260 is switched to the on state, the power transmission settingclutch mechanism 270 enters the state in which HST power transmission isset, and the shift power transmission device 220 is set to HST powertransmission. When the HMT clutch 255 is switched to the on state, andthe HST clutch 260 is switched to the off state, the power transmissionsetting clutch mechanism 270 enters the state in which HMT powertransmission is set, and the shift power transmission device 220 is setto HMT power transmission.

FIG. 30 is a front view in vertical section of the shift powertransmission device 220 during HMT power transmission. As shown in thisfigure, in the shift power transmission device 220, when the HMT clutch255 is switched to the on state, and the HST clutch 260 is switched tothe off state, drive force from the input shaft 222 (drive force fromthe engine 208) is inputted to the carrier 241 of the planetary powertransmission section 240 via the power train 250, drive force input fromthe input shaft 222 is subjected to speed change by the continuouslyvariable shift section 230, the speed-changed drive force output fromthe motor shaft 233 a is inputted to the sun gear 242 of the planetarypower transmission section 240, the planetary power transmission section240 combines the drive force from the engine 208 that is inputted fromthe input shaft 222 with the speed-changed drive force input from thecontinuously variable shift section 230 so as to generate combined driveforce, and the combined drive force output from the ring gear 244 of theplanetary power transmission section 240 is transmitted to the endportion of the output rotary member 224 via the planet-side interlockingmember 226 and the output-side interlocking member 227, and then outputfrom the output rotary member 224 to the traveling transmission 213.

FIG. 31 is a front view in vertical section of the shift powertransmission device 220 during HST power transmission. As shown in thisfigure, in the shift power transmission device 220, when the HMT clutch255 is switched to the off state, and the HST clutch 260 is switched tothe on state, drive force input from the input shaft 222 is subjected tospeed change by the continuously variable shift section 230, and thespeed-changed drive force output from the motor shaft 233 a istransmitted to the end portion of the output rotary member 224 via thepower transmission shaft 223, the HST clutch 260, the planet-sideinterlocking member 226, and the output-side interlocking member 227,and then output from the output rotary member 224 to the travelingtransmission 213.

When HST power transmission is set, the power transmission settingclutch mechanism 270 is in the state where power transmission from theinput shaft 222 to the carrier 241 of the planetary power transmissionsection 240 is cut off, the sun gear 242 is interlocked to the motorshaft 233 a via the power transmission shaft 223 so as to be capable ofin-unison rotation, and the ring gear 244 is interlocked to the motorshaft 233 a via the planet-side interlocking member 226, the clutchmember 261, the sun gear 242, and the power transmission shaft 223 so asto be capable of in-unison rotation. Accordingly, the sun gear 242, thecarrier 241, and the ring gear 244 of the planetary power transmissionsection 240 rotate in unison with the motor shaft 233 a, and in theshift power transmission device 220, during HST power transmission,output from the motor shaft 233 a of the continuously variable shiftsection 230 is transmitted to the output rotary member 224 withoutautorotation of the planet gears 243 occurring, that is to say, withoutrelative rotation of the sun gear 242 and the planet gears 243 occurringor relative rotation of the planet gears 243 and the ring gear 244occurring.

FIG. 33 is a graph (speed line diagram) showing output characteristicsof the shift power transmission device 220 during no-load driving, inwhich the output rotary member 224 is driven without being subjected totraveling load as driving load. A speed line indicating the rotationalspeed of the output rotary member 224 is shown on the vertical axis inthis graph. An operation position line L that passes through theposition at which the rotational speed plotted on the vertical axis iszero “0”, and that indicates the position of the swash plate of thehydraulic pump 232 configuring the continuously variable shift section230 is shown on the horizontal axis. Here, “n” on the operation positionline L indicates the neutral position of the swash plate 232 b at whichthe continuously variable shift section 230 is put into the neutralstate. Also, “a” on the operation position line L is the set forwardhigh-speed position, which is set as the maximum speed position on theforward side of the swash plate 232 b, which is for switching betweenthe HST power transmission setting and the HMT power transmissionsetting during no-load driving. Also, “+max” on the operation positionline L is the actual forward maximum speed position of the continuouslyvariable shift section 230, which is the swash plate angular positionthat is actually achieved by the swash plate 232 b of the hydraulic pump232 when the continuously variable shift section 230 is shifted to theoperation limit on the forward high speed side. In a simpleconfiguration in which rotation of the motor shaft 233 a is inputted tothe planet terminal without being accelerated/decelerated, the setforward high-speed position “a” is set to a position in front of theactual forward maximum speed position “+max” in order to maintain speedcontinuity at the point where there is a switch between HST powertransmission and HMT power transmission. Also, “−max” on the operationposition line L is the set reverse high-speed position, which is set asthe maximum speed position on the reverse side of the swash plate 232 b,which is operated in accordance with shift control. The set reversehigh-speed position “−max” is set to the same position as the swashplate angular position that is actually achieved by the swash plate 232b of the hydraulic pump 232 when the continuously variable shift section230 is shifted to the operation limit on the reverse high speed side.

A shift line S shown in FIG. 33 is a no-load HST shift line (referred tohereinafter as the HST shift line S) that indicates change in therotational speed of the output rotary member 224 when the shift powertransmission device 220 is shifted during HST power transmission in thestate in which the accelerator of the engine 208 is set such that a setconstant speed of drive force is output, and a shift line M is a no-loadHMT shift line (referred to hereinafter as the HMT shift line M) thatindicates change in the rotational speed of the output rotary member 224when the shift power transmission device 220 is shifted during HMT powertransmission in the state in which the accelerator of the engine 208 isset such that a set constant speed of drive force is output.

As shown in FIG. 33, when the HMT clutch 255 is controlled so as to beswitched to the off state and the HST clutch 260 is controlled so as tobe switched to the on state, HST power transmission is set, and in thestate in which the HST power transmission setting is maintained, if thecontinuously variable shift section 230 is shifted from the neutralposition “n” toward the set forward high-speed position “a”, therotational speed of the output rotary member 224 steplessly increasesfrom zero “0” to the forward side along a forward range SF of the HSTshift line S, and when the continuously variable shift section 230reaches the set forward high-speed position “a”, the rotational speed ofthe output rotary member 224 reaches a first forward intermediate speed“V1”.

When the continuously variable shift section 230 reaches the set forwardhigh-speed position “a”, the HMT clutch 255 is controlled so as to beswitched from the off state to the on state, and the HST clutch 260 iscontrolled so as to be switched from the on state to the off state, thussetting HMT power transmission instead of HST power transmission, and inthe state in which the HMT power transmission setting is maintained, ifthe continuously variable shift section 230 is shifted from the setforward high-speed position “a” toward the neutral position “n”, therotational speed of the output rotary member 224 steples sly increasesfrom the first forward intermediate speed “V1” along a low speed rangeML of the HMT shift line M, and when the continuously variable shiftsection 230 reaches the neutral position “n”, the rotational speed ofthe output rotary member 224 reaches a second forward intermediate speed“V2”. In the state in which the HMT power transmission setting ismaintained, if the continuously variable shift section 230 is shiftedfrom the neutral position “n” toward the set reverse high-speed position“−max”, the rotational speed of the output rotary member 224 steplesslyincreases from the second forward intermediate speed “V2” along a highspeed range ML of the HMT shift line M, and when the continuouslyvariable shift section 230 reaches the set reverse high-speed position“−max”, the rotational speed of the output rotary member 224 reaches aforward maximum speed “V3”

In the state in which the HST power transmission setting is maintained,if the continuously variable shift section 230 is shifted from theneutral position “n” toward the set reverse high-speed position “−max”,the rotational speed of the output rotary member 224 steplesslyincreases from zero “0” to the reverse side along a reverse range SR ofthe HST shift line S, and when the continuously variable shift section230 reaches the set reverse high-speed position “−max”, the rotationalspeed of the output rotary member 224 reaches a reverse maximum speed“VR”.

The angle of inclination B of the HMT shift line M relative to theoperation position line L is set as follows in order for the drive forcethat is to be output in the shift state corresponding to the high speedrange MH of the HMT shift line M to be drive force with a rotationalspeed that is appropriate for location change traveling, in order forthe drive force that is to be output in the shift state corresponding tothe low speed range ML of the HMT shift line M to be drive force with arotational speed that is appropriate for task traveling, and in order toobtain speed-changed drive force with minimal loss that accompanies thespeed change of drive force input from the engine 208 when employing acontinuously variable shift section 230 whose hydraulic pump 232 has thesmallest possible discharge capacity.

A shift line extension line ME shown in FIG. 33 is an extension of theHMT shift line M toward the operation position line L, and a position“P” on the operation position line L is the intersection position wherethe shift line extension line ME and the operation position line Lintersect. Assuming that the swash plate 232 b of the hydraulic pump 232of the continuously variable shift section 230 can be tilted beyond theactual forward maximum speed position “+max”, which is the farthest tiltposition on the forward side that can actually be reached, to theintersection position “P”, letting “N” be the value of the virtual angleof inclination achieved by the swash plate 232 b when tilted to theintersection position “P”, and letting “X” be the value of the actualhighest swash plate angle that is actually achieved in the hydraulicpump 232 of the continuously variable shift section 230 when it isshifted to the actual forward maximum speed position “+max”, the angleof inclination B of the HMT shift line M relative to the operationposition line L is set to the angle of inclination that corresponds tothe case where N is two times the value of X (N/X=2.0). The settingcorresponding to N/X=2.0 depends on the setting of the dischargecapacity of the hydraulic pump 232 and the setting of the gear powertransmission ratio in the planetary power transmission section 240 andmechanical power transmission portions other than the planetary powertransmission section 240.

The angle of inclination B of the HMT shift line M relative to theoperation position line L is set to the angle of inclination at whichthe rotational speed of the output rotary member 224 at the forwardmaximum speed “V3” is greater than or equal to two times the rotationalspeed of the output rotary member 224 at the first forward intermediatespeed “V1”.

The setting corresponding to N/X=2.0 is based on the evidence describedbelow.

When the output rotation of the continuously variable shift section 230is zero and the output rotational speed is V2, all of the drive force isoutputted without passing through the continuously variable shiftsection 230. At the virtual swash plate angle position (P), at which theoutput rotation is zero, the drive force at the output rotational speedV2 passes through the continuously variable shift section 230 and isreturned to the drive side, and output becomes zero. In other words,mechanical transmission power that does not pass through thecontinuously variable shift section 230 and power from the continuouslyvariable shift section 230 (referred to hereinafter as HST power) canceleach other out. In actuality, the virtual swash plate angle position (P)is a virtual position, and therefore giving consideration to the factthat the actual maximum angle of inclination X=1 when the continuouslyvariable shift section 230 is at the actual forward maximum speedposition “+max”, since the rotational speed is 1/N, the HST power is 1/Ntimes the mechanical transmission power that does not pass through thecontinuously variable shift section 230.

Letting KM be the mechanical efficiency of mechanical transmissionpower, and letting KH be the power that passes through the continuouslyvariable shift section 230, the output power is a constant mechanicalpower ±HST power, and the overall efficiency achieved by the shift powertransmission device 220 is calculated as shown below when thecontinuously variable shift section 230 is at the neutral position “n”.(1+0×1/N)/(1/KM+0×1/N/KH)=KM

When the continuously variable shift section 230 is at the set reversehigh-speed position “−max”:(1+1/N)/(1/KM+1/N/KH)=KM?KH(N+1)/(KM+KH?N)

When the continuously variable shift section 230 is at the actualforward maximum speed position “+max”:(1?1/N)/(1/KM?1/N?KH)=KM(N?1)/(N?KM?KH)

According to these calculations, the higher N is, the greater theefficiency can be improved.

FIG. 34 is an illustrative diagram showing the relationship betweenoverall efficiency and shift positions when varying the value N/X. Theoverall efficiency shown here was approximated as described above,assuming that KM=0.95 and KH=0.7, and using N/X=1.0, N/X=2.0, andN/X=3.0.

The horizontal axis shown in FIG. 34 indicates the shift position, andthe shift position on the horizontal axis is the ratio of the outputrotational speed when the continuously variable shift section 230 isshifted to an arbitrary shift position during forward-side HST powertransmission and HMT power transmission to the output rotational speedwhen the continuously variable shift section 230 is shifted to the setreverse high-speed position “−max”. In other words, letting Vn be therotational speed of drive force that is outputted when the continuouslyvariable shift section 230 is shifted to an arbitrary shift positionduring forward-side HST power transmission and HMT power transmission,Vn/V3 is the shift position on the horizontal axis. A vertical line Dshown in FIG. 34 is a line indicating the maximum speed during HST powertransmission when N/X=2.0, which is Vn/V3=0.33 (between 0.2 and 0.4). Avertical line E shown in FIG. 34 is a line indicating the speed when theswash plate of the hydraulic pump 232 is at the neutral position duringHMT power transmission when N/X=2.0, which is Vn/V3=0.67 (between 0.6and 0.8). Accordingly, the set forward high-speed position “a” of thecontinuously variable shift section 230 is a position between 0.2 and0.4 on the horizontal axis, and the neutral position “n” of the shift230 is a position between 0.6 and 0.8 on the horizontal axis.

An efficiency line K shown in FIG. 34 indicates the overall efficiencyof the continuously variable shift section 230. An efficiency line K1shown in FIG. 34 indicates the overall efficiency approximated usingN/X=1.0, an efficiency line K2 indicates the overall efficiencyapproximated using N/X=2.0, and an efficiency line K3 indicates theoverall efficiency approximated using N/X=3.0.

Between the vertical line D and the vertical line E, the overallefficiency is favorable when N/X=1.0, but since the output is also highon the high speed side, the amount of power loss increases, and even asmall difference in efficiency cannot be ignored. In consideration ofpower loss obtained by multiplying output power by the rate of loss,approximately N/X=1.8 is the minimum value. Although the mostappropriate value in terms of power loss has a wide range when the N/Xvalue is low around N/X=1.8, N/X=2.0 is the most appropriate value forreducing the size of the continuously variable shift section 230. If N/Xis approximately 1.5 to 2.5 in order to achieve balance, it is possibleto both realize higher efficiency in the high speed range and achieve a38% reduction in the size of the continuously variable shift section230. The output rotation of the planetary power transmission section 240during HMT power transmission at this time can also be designed so as tobe in a realistic range that does not exceed 10000 rpm. When the shiftpower transmission device 220 is an independent unit, lowering theextent of rotational speed from the drive source enables reducing theinfluence of torque loss caused by output portion sealing and the like,and therefore deceleration of 2.5 to 3 is performed by the planetarypower transmission section 240, which also makes the configurationrealistically more readily achievable. When employing the simple powertransmission setting clutch mechanism 270 as described above, thesetting of N/X=1.5 to 2.5 is advantageous in terms of high efficiencyand reducing the size of the continuously variable shift section 230.

FIG. 35 is an illustrative diagram showing the relationship between thevalue of N/X and size reduction of the continuously variable shiftsection 230. The horizontal axis in FIG. 35 indicates the value of N/X.A line F shown in FIG. 35 indicates the ratio “W” of the HST power (1/N)to the total power (1+1/N). The higher this ratio “W” is, the larger thedischarge capacity of the hydraulic pump 232 needs to be, and the largerthe continuously variable shift section 230 needs to be.

The size of the continuously variable shift section 230 can be madesmaller when drive force over a predetermined shift range is to beobtained by output from the planetary power transmission section 240than when it is to be obtained by output from the continuously variableshift section 230, and a line G shown in FIG. 35 indicates therelationship between the value of N/X and the extent to which the sizeof the continuously variable shift section 230 can be reduced.

Specifically, assuming that the actual maximum tilt position “+max” isthe point at which there is a switch between HST power transmission andHMT power transmission, the ratio of the maximum speed during HMT powertransmission (forward maximum speed “V3”) to the maximum speed duringHST power transmission is similarly calculated as (N+1)/(N?1)=Z. Z is5.0 when N/X=1.5, is 3.0 when N/X=2.0, is 2.3 when N/X=2.5, and is 2.0when N/X=3.0. The values indicated on the vertical axis in FIG. 35 arethe value of 1/Z.

The higher the value of Z is, the greater the shift range that can beobtained by HMT power transmission is, the smaller the shift range thatneeds to be obtained by HST power transmission is, and the greater thesize of the continuously variable shift section 230 can be reduced, butif the discharge capacity of the hydraulic pump 232 is too small, driveproblems will occur, such as the relief circuit opening and operating.Accordingly, by employing N/X=2.0, which achieves an intersectionbetween the line F and the line G, it is possible to obtain a shiftpower transmission device 220 capable of shift power transmission thatavoids the occurrence of drive problems in the continuously variableshift section 230, while also achieving a forward maximum speed “V3” anda second forward intermediate speed “V2” during HMT power transmissionthat are speeds necessary for location change and task, and alsoachieving a reduction in the size of the continuously variable shiftsection 230.

FIG. 37 is a graph (speed line diagram) showing output characteristicsof the shift power transmission device 220 during no-load driving, inwhich the output rotary member 224 is driven without being subjected totraveling load as driving load, and also output characteristics of theshift power transmission device 220 during load driving, in which theoutput rotary member 224 is driven in the state of being subjected totraveling load as driving load. FIG. 39 is an illustrative diagramshowing switching of the setting from HST power transmission to HMTpower transmission. The vertical axis and the horizontal axis in FIGS.37 and 39 are the same as the vertical axis and the horizontal axis inthe graph shown in FIG. 31. Also, “n”, “a”, and “−max” shown in FIGS. 37and 39 are the same as “n”, “a”, and “−max” shown in the graph in FIG.31.

A shift line SA shown in FIG. 37 is a load HST shift line (referred tohereinafter as the HST shift line SA) that indicates change in therotational speed of the output rotary member 224 in the state in whichthe accelerator of the engine 208 is set such that a set constant speedof drive force is output, a traveling load is applied to the outputrotary member as the driving load with a set value, and the shift powertransmission device 220 is driven while HST power transmission is set. Ashift line MA shown in FIG. 37 is a load HMT shift line (referred tohereinafter as the HMT shift line MA) that indicates change in therotational speed of the output rotary member 224 in the state in whichthe accelerator of the engine 208 is set such that a set constant speedof drive force is output, a traveling load is applied to the outputrotary member as the driving load with a set value, and the shift powertransmission device 220 is driven while HMT power transmission is set.Since the HST shift line SA corresponds to the state in which the swashplate 232 b is subjected to driving load, the angle of inclination ofthe HST shift line SA relative to the operation position line L issmaller than the angle of inclination of the HST shift line S relativeto the operation position line L. Since the HMT shift line MAcorresponds to the state in which the swash plate 232 b is subjected todriving load, the low speed side of the HMT shift line MA is shifted tothe low speed side of the HMT shift line M.

When provided for the motor shaft 233 for when switching the settingfrom HST power transmission to HMT power transmission, a horizontal lineL1 shown in FIG. 37 indicates the rotational speed of the motor shaft233 a at which in-unison rotation of the sun gear 242, the carrier 241,and the ring gear 244 is achieved (in-unison rotation achievement speed“V”) in the planetary power transmission section 240 at the point intime when switching is completed by the clutch mechanism 270 forswitching the setting from HST power transmission to HMT powertransmission, and drive force from the engine 208 is transmitted to theplanetary power transmission section 240. This rotational speed of themotor shaft 233 a is the same as the rotational speed “V1” of the outputrotary member 224. During HST power transmission and no-load driving,the continuously variable shift section 230 achieves the in-unisonrotation achievement speed “V” when the swash plate 232 b of thehydraulic pump 232 is set to the set forward high-speed position “a”.

FIG. 36 is a block diagram showing a shift operation apparatus 271 thatperforms shift operations on the shift power transmission device 220. Asshown in this figure, the shift operation apparatus 271 includes acontrol apparatus 272 that is linked to a shift operation section 230 aof the continuously variable shift section 230 and operation sections255 a and 260 a of the HMT clutch 255 and the HST clutch 260, as well asa shift operation device 277, an engine speed sensor 274, a swash plateangle sensor 275, and an output speed sensor 276 that are linked to thecontrol apparatus 272.

The shift operation section 230 a is configured by an electricalactuator or a hydraulic actuator that operates so as to change the angleof the swash plate 232 b of the hydraulic pump 232 in the continuouslyvariable shift section 230. The operation section 255 a of the HMTclutch 255 is configured by an operation valve that is connected to thehydraulic piston 258 via an operation oil path formed inside the inputshaft 222, and by operating the hydraulic piston 258 so as to cause theclutch member 256 to slide, the operation section 255 a switches the HMTclutch 255. The operation section 260 a of the HST clutch 260 isconfigured by an operation valve that is connected to the oil chamber ofthe clutch member 261 via an operation oil path formed inside the powertransmission shaft 223, and by supplying/discharging operation oilto/from the oil chamber of the clutch member 261, the operation sectiont260 a causes the clutch member 261 to slide so as to switch the HSTclutch 260.

The shift operation device 277 is configured by a shift lever providedin the driving section 202 so as to be capable of being swung in thefront/rear direction of the traveling body, and is swung to a neutralposition “277N”, in a forward operation range “277F” that extends fromthe neutral position “277N” toward the front of the device body, and ina reverse operation range “277W” that extends from the neutral position“277N” toward the rear of the device body. The shift operation device277 is linked to the control apparatus 272 via a shift detection sensor273 that detects the operation position of the shift operation device277. The shift detection sensor 273 is configured by a rotationpotential meter that is interlocked to the rotation operation shaft ofthe shift operation device 277, and when the shift operation device 277is swung, the shift detection sensor 273 operates, and a shiftinstruction is outputted from the shift detection sensor 273 to thecontrol apparatus 272 in the form of an electrical signal.

The engine speed sensor 274 detects the rotational speed of the engine208, and outputs this detection result to the control apparatus 272. Theswash plate angle sensor 275 detects the angle of the swash plate of thehydraulic pump 232 of the continuously variable shift section 230, andoutputs this detection result to the control apparatus 272. The outputspeed sensor 276 detects the rotational speed of the output rotarymember 224 as the output rotational speed of the shift powertransmission device 220, and outputs this detection result to thecontrol apparatus 272.

The control apparatus 272 is configured using a microcomputer, andincludes a shift control module 278 and a shift swash plate anglesetting module 280.

The shift swash plate angle setting module 280 is configured by astorage section provided in the control apparatus 272. The shift swashplate angle setting module 280 receives a swash plate angle forperforming control for switching the setting from HST power transmissionto HMT power transmission, as a pre-set set shift swash plate angle “c”.

Based on detection information from the engine speed sensor 274, theshift control module 278 detects the speed of the engine 208 whoseaccelerator has been set, performs shift control on the hydraulic pump232 based on this detection result, a shift instruction from the shiftoperation device 277, and detection information from the swash plateangle sensor 275 and the output speed sensor 276, and also controls theswitching of the HST clutch 260 and the HMT clutch 255 of the clutchmechanism 270.

FIG. 38 is a flowchart showing setting switching control for switchingthe setting from HST power transmission to HMT power transmission. Asshown in this figure, the shift control module 278 compares the detectedswash plate angle from the swash plate angle sensor 275 and the setshift swash plate angle “c” from the shift swash plate angle settingmodule 280, and determines whether or not the detected swash plate angleis equal to the set shift swash plate angle “c”, thus determiningwhether or not the swash plate angle sensor 275 detected a swash plateangle that is equal to the set shift swash plate angle “c”. In the caseof determining that the swash plate angle sensor 275 detected a swashplate angle that is equal to the set shift swash plate angle “c”, theshift control module 278 performs control for switching the HST clutch260 of the clutch mechanism 270 to the off state, and performs controlfor switching the HMT clutch 255 to the on state, thus switching thesetting from HST power transmission to HMT power transmission.

Accordingly, in the state in which the accelerator of the engine 208 isset such that drive force with a constant rotational speed is output,when the shift operation device 277 is operated in the reverse operationrange “277W”, to the neutral position “277N”, and in the forwardoperation range “277F”, the shift control module 278 performs controlfor switching the setting of the shift power transmission device 220between HST power transmission and HMT power transmission and performsshift control on the hydraulic pump 232, thus causing the traveling bodyto travel in forward and reverse, as well as traveling while changingspeed in forward and reverse, and stopping.

Specifically, when the shift operation device 277 is operated to theneutral position “277N” or the low speed range portion of the reverseoperation range “277R” or the forward operation range “277F”, the shiftcontrol module performs control for switching the HMT clutch 255 and theHST clutch 260 based on a shift instruction from the shift operationdevice 277 and setting information from the shift swash plate anglesetting module 280, and thus the shift power transmission device 220 isset to HST power transmission. When the shift operation device 277 isoperated to the high speed range portion of the forward operation range“277F”, the shift control module performs control for switching the HMTclutch 255 and the HST clutch 260 based on a shift instruction from theshift operation device 277 and setting information from the shift swashplate angle setting module 280, and thus the shift power transmissiondevice 220 is set to HMT power transmission.

If the shift operation device 277 is operated to the neutral position“277N”, the shift control module 278 moves the swash plate 232 b of thehydraulic pump 232 to the neutral position “n” based on a shiftinstruction from the shift operation device 277, the continuouslyvariable shift section 230 enters the neutral state, and output from theshift power transmission device 220 is stopped.

If the shift operation device 277 is moved in the low speed rangeportion of the forward operation range “277F”, the shift control module278 tilts the swash plate 232 b of the hydraulic pump 232 on the forwardside of the neutral position “n” based on a shift instruction from theshift operation device 277 and detection information from the outputspeed sensor 276, and the speed of the drive force outputted by theshift power transmission device 220 changes along the forward range ofthe load HST shift line SA.

If the shift operation device 277 is moved in the high speed range ofthe forward operation range “277F”, the shift control module 278 tiltsthe swash plate 232 b of the hydraulic pump 232 over the forward sideand the reverse side based on a shift instruction from the shiftoperation device 277 and detection information from the output speedsensor 276, and the speed of the drive force outputted by the shiftpower transmission device 220 changes along the load HMT shift line MA.

If the shift operation device 277 is moved in the reverse operationrange “277R”, the shift control module 278 tilts the swash plate 232 bof the hydraulic pump 232 on the reverse side of the neutral position“n” based on a shift instruction from the shift operation device 277 anddetection information from the output speed sensor 276, and the speed ofthe drive force outputted by the shift power transmission device 220changes along the reverse range of the load HST shift line SA.

FIG. 44 is an illustrative diagram showing switching from HST powertransmission to HMT power transmission in a comparative example. Ahorizontal line L1 shown in FIG. 44 is the same as the horizontal lineL1 shown in FIG. 37.

As shown in FIGS. 37 and 44, the time when the rotational speed of themotor shaft 233 a increasing along the HST shift line S reaches thein-unison rotation achievement speed “V” is the point in time indicatedby the intersection between the HST shift line S and the HMT shift lineM, and the swash plate angle of the hydraulic pump 232 at this point intime is the no-load swash plate angle “a” achieved at the forward sethigh speed position “a”. The time when the rotational speed of the motorshaft 233 a increasing along the HST shift line SA reaches the in-unisonrotation achievement speed “V” is the point in time indicated by theintersection “X” between the HST shift line SA and the horizontal lineL1, the swash plate angle of the hydraulic pump 232 at this point intime is the load swash plate angle “b”, and this load swash plate angle“b” is a swash plate angle reached when the swash plate 232 b is tiltedon the high speed side of the no-load swash plate angle “a”.

When the setting is switched from HST power transmission to HMT powertransmission at the point in time when the rotational speed of the motorshaft 233 a increasing along the HST shift line SA reaches the in-unisonrotation achievement speed “V”, the output speed of the output rotarymember 224 changes from the in-unison rotation achievement speed “V” tothe rotational speed “V0” that is lower than the in-unison rotationachievement speed “V” and corresponds to the intersection “Y” betweenthe HMT shift line MA and a vertical line that passes through theintersection “X” and the position corresponding to the load swash plateangle “b”. In other words, when the setting is switched from HST powertransmission to HMT power transmission, after the switch, the travelingspeed decreases from the speed corresponding to the in-unison rotationachievement speed “V” to the speed that corresponds to the output speed“V0”.

FIG. 39 is an illustrative diagram showing setting switching from HSTpower transmission to HMT power transmission performed by the shiftcontrol module 278 according to this embodiment of the presentinvention. As shown in this figure, the set shift swash plate angle “c”is set as a swash plate angle between the no-load swash plate angle “a”and the load swash plate angle “b”. More specifically, the set shiftswash plate angle “c” is set as a swash plate angle that is between theload swash plate angle “b” and the intersection swash plate angle “d”,which corresponds to the intersection “W” between the HST shift line SAand the HMT shift line MA. This swash plate angle is closer to theintersection swash plate angle “d” than the load swash plate angle “b”.

Accordingly, when the rotational speed of the motor shaft 233 aincreasing along the HST shift line SA reaches the rotational speed “VS”that corresponds to the intersection “S1” between the HST shift line SAand the vertical line that passes through the set shift swash plateangle “c”, the shift control module 278 performs control for switchingthe setting from HST power transmission to HMT power transmission.Accordingly, the rotational speed of the output rotary member 224, whichis the output speed of the shift power transmission device 220immediately after the setting is switched from HST power transmission toHMT power transmission, is the rotational speed “VM” that corresponds tothe intersection “M1” between the HMT shift line MA and the verticalline that passes through the intersection “S1”. The control performed bythe shift control module 278 for switching the setting from HST powertransmission to HMT power transmission is performed when the shiftoperation device 277 is located in the central portion of the forwardoperation range “277F”.

Specifically, the rotational speed “VS” of the motor shaft 233 a that isthe output speed of the continuously variable shift section 230 when thesetting is to be switched from HST power transmission to HMT powertransmission is a rotational speed that is lower than the in-unisonrotation achievement speed “V”. The rotational speed of the outputrotary member 224 that is the output speed of the shift powertransmission device 220 immediately after the setting is switched fromHST power transmission to HMT power transmission is higher than therotational speed “V0” of the output rotary member 224 immediately aftera switch when the setting is switched from HST power transmission to HMTpower transmission due to the output speed of the continuously variableshift section 230 reaching the in-unison rotation achievement speed “V”.The amount of change in the traveling speed that accompanies a switchfrom HST power transmission to HMT power transmission corresponds to thedifference in speed between the output speed “VS” immediately before theswitch and the output speed “VM” immediately after the switch, and theswitch from an HST power transmission speed range to an HMT powertransmission speed range is performed while causing this difference inspeed to be smaller than the difference in speed between the outputspeed “V” immediately before the switch and the output speed “V0”immediately after the switch when the switching of the setting from HSTpower transmission to HMT power transmission is performed based on theoutput speed.

First Alternative Embodiment

FIG. 40 is a block diagram showing the shift operation apparatus 271according to a first alternative embodiment. As shown in this figure, inthe shift operation apparatus 271 according to the first alternativeembodiment, the shift swash plate angle setting module 280 is providedwith an adjustment section 281 that is linked to the control apparatus272.

The adjustment section 281 is configured by a rotation potential meterthat includes a rotation operation device 281 a. When an adjustmentoperation is performed using the rotation operation device 281 a, thesetting of the swash plate angle of the hydraulic pump 232 for whenswitching the setting from HST power transmission to HMT powertransmission is changed by the adjustment section 281 to the high speedside or the low speed side, and the changed set shift swash plate angleis outputted to the control apparatus 272, and thus the shift swashplate angle setting module 280 is adjusted such that the new set shiftswash plate angle from the adjustment section 281 is inputted to theshift swash plate angle setting module 280 in place of the set shiftswash plate angle that was previously input.

Specifically, when the shift swash plate angle setting module 280 isadjusted by the adjustment section 281, as shown in FIG. 41 for example,the swash plate angle “c” of the hydraulic pump 232 that corresponds tothe intersection “W” between the HST shift line SA and the HMT shiftline MA is set as the set shift swash plate angle by the shift swashplate angle setting module 280, and it is possible to perform controlfor switching the setting from HST power transmission to HMT powertransmission in the state in which the rotational speed “VS1” of themotor shaft 233 a for when switching the setting from HST powertransmission to HMT power transmission and the rotational speed “VM1” ofthe output rotary member 224 immediately after switching the settingfrom HST power transmission to HMT power transmission are the samerotational speed.

Second Alternative Embodiment

FIG. 42 is a block diagram showing the shift operation apparatus 271according to a second alternative embodiment. As shown in this figure,the shift operation apparatus 271 according to the second alternativeembodiment includes a storage section 283 that receives map controldata.

The storage section 283 receives in advance and stores map control datathat includes a detected swash plate angle that is detected by the swashplate angle sensor 275 when the shift power transmission device 220 isto be driven during HST power transmission and load driving, anappropriate corresponding HST shift line that corresponds to thedetected swash plate angle, and an appropriate corresponding HMT shiftline that corresponds to the corresponding HST shift line.

FIG. 43 is an illustrative diagram showing control for switching thesetting from HST power transmission to HMT power transmission in theshift operation apparatus 271 according to the second alternativeembodiment. As shown in this figure, in the shift swash plate anglesetting module 280, when the shift power transmission device 220 isdriven during HST power transmission and load driving, up to the timewhen the setting is switched from HST power transmission to HMT powertransmission, detection information is continuously received from theswash plate angle sensor 275, and each time detection information isreceived from the swash plate angle sensor 275, a calculated HST shiftline SA1 for HST power transmission and load driving that corresponds tothe detected swash plate angle from the swash plate angle sensor 275 iscalculated and set based on the detection information from the swashplate angle sensor 275 and the map control data input to the storagesection 283, an appropriate calculated HMT shift line MA1 thatcorresponds to the calculated HST shift line SA1 is calculated and set,the swash plate angle achieved by the hydraulic pump 232 in the shiftstate for outputting speed-changed drive force at a speed thatcorresponds to the intersection W1 between the calculated HST shift lineSA1 and the calculated HMT shift line MA1 is determined, and thedetermined swash plate angle is set as the set shift swash plate angle“c”.

Accordingly, in the shift control module 278, even if the drive loadchanges during traveling, a set shift swash plate angle “c” that isoptimum for switching the setting from HST power transmission to HMTpower transmission and for preventing a change in traveling speed thataccompanies the switching of the setting from HST power transmission toHMT power transmission is given as the set shift swash plate angle, theswitch from an HST power transmission speed range to an HMT powertransmission speed range is performed in the state where the switch isnot accompanied by a change in speed regardless of the change in driveload, and thus the shift from an HST power transmission speed range toan HMT power transmission speed range is performed without causing shiftshock or unpleasantness.

Other Alternative Embodiments

(1) Although the above-described embodiment gives the example where theclutch mechanism 270 is configured by a meshing type HMT clutch 255 andHST clutch 260, an implementation is possible in which the clutchmechanism 270 is configured by a friction HMT clutch 255 and HST clutch260.

(2) Although the above-described embodiment gives the example where thecontinuously variable shift section 230 is configured to include afixed-capacity hydraulic motor 233, an implementation is possible inwhich the continuously variable shift section 230 is configured toinclude a variable displacement hydraulic motor.

Fourth Embodiment

Next, a fourth embodiment will be described with reference to FIGS. 45to 54.

As shown in FIG. 45, the combine, which performs the task of harvestingrice, barley, and the like, is configured to be self-propelled with apair of right and left crawling travel apparatuses 301, and isconfigured to include a traveling body equipped with a riding drivingsection 302, a reaping section 304 coupled to the front portion of abody frame 303 of the traveling body, a threshing apparatus 305 providedso as to be arranged rearward of the reaping section 304 on the rearside of the body frame 303, and a grain tank 306 provided so as to bearranged to the side of the threshing apparatus 305 on the rear side ofthe body frame 303.

Specifically, the reaping section 304 includes a reaping section frame304 a that extends forward from the front portion of the body frame 303in a vertically swingable manner, and when the reaping section frame 304a is swung by an elevating cylinder 307, the reaping section 304 movesup/down between a lowered operating position at which a divider 304 b,which is provided at the front edge portion of the reaping section 304,is lowered close to the ground, and a raised non-operating position atwhich the divider 304 b is raised high above the ground. When thetraveling body is caused to travel with the reaping section 304 loweredto the lowered operating position, the reaping section 304 operates suchthat reaping-target planted stalks are guided to a raising path by thedivider 304 b, the planted stalks that were guided to the raising pathare reaped by a clipper-type reaping apparatus 304 d while being raisedup by a raising apparatus 304 c, and the reaped stalks are supplied tothe threshing apparatus 305 by a supplying apparatus 304 e. In thethreshing apparatus 305, the reaped stalks are conveyed from thesupplying apparatus 304 e toward the rear of the apparatus body withtheir base sides clamped by a threshing feed chain 305 a, the eartip-sides of the reaped stalks are supplied to a handling compartment(not shown) where they are subjected to reaping processing, and thereaped grain is fed to the grain tank 306.

The combine is configured such that an engine 308 is provided underneatha driver seat 302 a provided in the driving section 302, and drive forceoutputted by the engine 308 is transmitted to the pair of right and lefttravel apparatuses 301 by a travel power transmission apparatus 310 thatincludes a transmission case 311 provided at the front edge portion ofthe body frame 303.

FIG. 46 is a front view of the schematic structure of the travel powertransmission apparatus 310. As shown in this figure, in the travel powertransmission apparatus 310, engine drive force from an output shaft 308a of the engine 308 is inputted to a shift power transmission device 320provided on the side of the upper end portion of the transmission case311 via a power train 312 provided with a power transmission belt 312 a.Output of the shift power transmission device 320 is inputted to atraveling transmission 313 provided inside the transmission case 311,then transmitted from a left-side steering clutch mechanism 314, whichis one of a pair of right and left steering clutch mechanisms 314included in the traveling transmission 313, to a drive shaft 301 a ofthe left-side travel apparatus 301, and also transmitted from theright-side steering clutch mechanism 314 to a drive shaft 301 a of theright-side travel apparatus 301.

The travel power transmission apparatus 310 includes a reapingtransmission 315 that is provided inside the transmission case 311, andoutput of the shift power transmission device 320 is inputted to thereaping transmission 315 and transmitted from a reaping output shaft 316to a drive shaft 304 f of the reaping section 304.

Next, the shift power transmission device 320 will be described.

As shown in FIGS. 47 and 48, the shift power transmission device 320 isconfigured to include a planetary shift section 320A, which is providedwith a shift case 321 whose side portion is coupled to the upper endside of the transmission case 311, and a hydrostatic continuouslyvariable shift section 330 that has a casing 331 coupled to the sideportion on the side opposite to the side on which the shift case 321 iscoupled to the transmission case 311.

The shift case 321 is configured to include a main case portion 321 athat accommodates a planetary power transmission section 340 and a powertrain 350, and a coupling case portion 321 b that accommodates aconnection portion between the continuously variable shift section 330and an input shaft 322 and a power transmission shaft 323, and thatcouples the shift case 321 with a port block 334 of the casing 331. Theshift case 321 is coupled to the transmission case 311 with a bulgingportion 321 c formed so as to bulge outward horizontally on the sideface of the lower portion of the main case portion 321 a where theoutput rotary member 324 is located. The size of the coupling caseportion 321 b in the up/down direction of the traveling body is smallerthan the size of the main case portion 321 a in the up/down direction ofthe traveling body. The main case portion 321 a is formed such that theshape in vertical section is vertically elongated when viewed in thefront/rear direction of the apparatus body, the casing 331 is formedsuch that the shape in vertical section is vertically elongated whenviewed in the front/rear direction of the apparatus body, the planetaryshift section 320A and the continuously variable shift section 330 arealigned in the horizontal direction of the apparatus body such that theshift power transmission device 320 has a small width overall in thehorizontal direction of the apparatus body, and the shift powertransmission device 320 is coupled to the lateral side of thetransmission case 311 in a compact state with respect to the left/rightdirection of the traveling body so as to not protrude outward laterally.Furthermore, a bulging portion 331B that supports a bearing of a motorshaft 333 a is formed on the side face of the lower portion of thecasing 331, thus making the shift power transmission device 320 evenmore compact. Also, an oil filter 320F is arranged facing upward on theupper face of the casing 331, and further compactness is achieved bypreventing the oil filter 320F from protruding outward laterally.

The planetary shift section 320A includes the input shaft 322 that isoriented in the horizontal direction of the apparatus body and isrotatably supported to the upper end side of the shift case 321, a powertransmission shaft 323 and a rotating shaft-type of output rotary member324 that are rotatably supported to the lower end side of the shift case321 parallel or substantially parallel to the input shaft 322, theplanetary power transmission section 340 that is supported to the powertransmission shaft 323, and the power train 350 provided so as to spanfrom the input shaft 322 to a carrier 341 of the planetary powertransmission section 340.

The input shaft 322 is arranged so as to be coaxially aligned with apump shaft 332 a of the continuously variable shift section 330. Theinput shaft 322 is configured such that on the side on which itprotrudes laterally outward from the shift case 321, it is coupled withan output shaft 308 a of the engine 308 via the power train 312, and onthe side opposite to the side coupled to the engine 308, it is coupledto the pump shaft 332 a of the continuously variable shift section 330so as to be capable of in-unison rotation therewith via a joint 322 a.The input shaft 322 receives engine drive force via the power train 312,and drives the hydraulic pump 332 of the continuously variable shiftsection 330 upon being driven by engine drive force.

The output rotary member 324 is arranged so as to be coaxially alignedwith a motor shaft 333 a of the continuously variable shift section 330on the same side of the continuously variable shift section 330 as theside on which the engine-coupled side of the input shaft 322 is located.The output rotary member 324 is configured such that on the side onwhich it protrudes laterally outward from the shift case 321, it isinterlocked with an input portion of the traveling transmission 313, andoutputs drive force from the planetary power transmission section 340and the continuously variable shift section 330 to the pair of right andleft travel apparatuses 301 via the traveling transmission 313.

The continuously variable shift section 330 is configured to include thehydraulic pump 332 whose pump shaft 332 a is rotatably supported to theupper end side of the casing 331, and the hydraulic motor 333 whosemotor shaft 333 a is rotatably supported to the lower end side of thecasing 331. The hydraulic pump 332 is configured by a variabledisplacement axial plunger pump, and the hydraulic motor 333 isconfigured by a variable displacement axial plunger motor. The hydraulicmotor 333 is driven by hydraulic oil that is discharged from thehydraulic pump 332 and supplied via an oil path formed inside the portblock 334. The continuously variable shift section 330 is supplied withreplenishing hydraulic oil by a charge pump 390 mounted to an endportion of the pump shaft 332 a. The charge pump 390 includes a rotor390 a attached to the pump shaft 332 a so as to be capable of in-unisonrotation therewith, and a pump casing 390 b that is removably coupled tothe casing 331.

Accordingly, the continuously variable shift section 330 switchesbetween the forward power transmission state, the reverse powertransmission state, and the neutral state by an operation for changingthe angle of a swash plate 332 b that the hydraulic pump 332 is providedwith. When the continuously variable shift section 330 is switched tothe forward power transmission state, engine drive force transmittedfrom the input shaft 322 to the pump shaft 332 a is converted intoforward drive force and output from the motor shaft 333 a, and when itis switched to the reverse power transmission state, engine drive forcetransmitted from the input shaft 322 to the pump shaft 332 a isconverted into reverse drive force and output from the motor shaft 333a, and thus engine drive force is subjected to stepless speed changingand output in both the forward power transmission state and the reversepower transmission state. When the hydraulic continuously variable shiftsection 330 is switched to the neutral state, output from the motorshaft 333 a is stopped.

The planetary power transmission section 340 is arranged so as to belocated between the motor shaft 333 a and the output rotary member 324on the same side of the continuously variable shift section 330 as theside on which the engine-coupled side of the input shaft 322 is located.The planetary power transmission section 340 includes a sun gear 342that is supported to the power transmission shaft 323, multiple planetgears 343 that are meshed with the sun gear 342, a ring gear 344 that ismeshed with the planet gears 343, and a carrier 341 that rotatablysupports the planet gears 343. The carrier 341 includes arm portions 341a that rotatably support the planet gears 343 with an extending endportion, and a tube shaft portion 341 b that is coupled to base sides ofthe arm portions 341 a, and the carrier 341 is rotatably supported tothe power transmission shaft 323 with the tube shaft portion 341 b via abearing.

The power transmission shaft 323 and the motor shaft 333 a are coupledto each other via a joint 323 a so as to be capable of in-unisonrotation, the power transmission shaft 323 and the sun gear 342 arecoupled via a spline structure so as to be capable of in-unisonrotation, and the sun gear 342 is interlocked with the motor shaft 333 aso as to be capable of in-unison rotation.

The ring gear 344 and the output rotary member 324 are interlocked so asto be capable of in-unison rotation, using an annular planet-sideinterlocking member 326 and an annular output-side interlocking member327 that are aligned axially with the power transmission shaft 323 andfit around it so as to be capable of relative rotation. Specifically,the planet-side interlocking member 326 includes multiple engaging armportions 326 a that extend radially from the outer circumferentialportion of the planet-side interlocking member 326 so as to be capableof in-unison rotation. The engaging arm portions 326 a are engaged withthe ring gear 344 at multiple locations, and the planet-sideinterlocking member 326 is interlocked with the ring gear 344 so as tobe capable of in-unison rotation. The output-side interlocking member327 is engaged with the planet-side interlocking member 326 using anengaging claw 327 a so as to be capable of in-unison rotation, isengaged with the output rotary member 324 using a spline structure so asto be capable of in-unison rotation, and is coupled to the planet-sideinterlocking member 326 and the output rotary member 324 so as to becapable of in-unison rotation. The planet-side interlocking member 326is supported to the power transmission shaft 323 via a bearing so as tobe capable of relative rotation. The output-side interlocking member 327is rotatably supported to the shift case 321 via a bearing.

The power train 350 is configured to include a power transmission gear352 that is supported to the input shaft 322 via a needle bearing so asto be capable of relative rotation in a state of being meshed with aninput gear 341 c of the carrier 341 that is provided so as to be capableof in-unison rotation with the tube shaft portion 341 b of the carrier341, and an HMT clutch 355 provided so as to span between the powertransmission gear 352 and the input shaft 322.

The HMT clutch 355 is configured to include a clutch member 356supported to the input shaft 322 so as to be capable of in-unisonrotation and sliding, and a clutch body 357 provided so as to spanbetween one end side of the clutch member 356 and a lateral side of thepower transmission gear 352. The clutch member 356 is caused to slide bya hydraulic piston 358 that is fit inside an end portion of the clutchmember 356. The clutch body 357 is configured as a meshing clutch thatswitches between an on state and an off state when a meshing clawprovided on the clutch member 356 and a meshing claw provided on thepower transmission gear 352 engage/disengage with each other.

When the clutch body 357 is switched to the on state, the HMT clutch 355is switched to the on state such that the input shaft 322 and the powertransmission gear 352 are interlocked so as to be capable of in-unisonrotation, and thus the HMT clutch 355 enters the state in which HMTpower transmission is set so that the carrier 341 of the planetary powertransmission section 340 and the input shaft 322 are interlocked.

When the clutch body 357 is switched to the off state, the HMT clutch355 is switched to the off state such that the interlocking of the inputshaft 322 and the power transmission gear 352 is cut off, and thus theHMT clutch 355 enters the state in which the HMT power transmissionsetting is canceled so that the interlocking of the carrier 341 of theplanetary power transmission section 340 and the input shaft 322 is cutoff.

Accordingly, in the planetary power transmission section 340, when theHMT clutch 355 is switched to the state in which HMT power transmissionis set, drive force from the input shaft 322 is inputted from a sitelocated between the engine-coupled side and the continuously variableshift section-coupled side of the input shaft 322 to the carrier 341 viathe power train 350. When the HMT clutch 355 is switched to the state inwhich the HMT power transmission setting is canceled, the planetarypower transmission section 340 enters a state in which interlocking ofthe carrier 341 with the input shaft 322 is cut off.

An HST clutch 360 that includes a clutch member 361 fit around the powertransmission shaft 323 is provided so as to span between the sun gear342 of the planetary power transmission section 340 and the planet-sideinterlocking member 326.

When hydraulic oil is supplied to an oil chamber formed on the innercircumferential side of the clutch member 361, the clutch member 361switches to an off position by being caused to slide toward the sun gear342 in resistance to an on biasing spring 362, and when hydraulic oil isdischarged from the oil chamber, the clutch member 361 switches to an onposition by being caused to slide toward the planet-side interlockingmember 326 by the on biasing spring 362. When the clutch member 361switches to the on position, a clutch claw 361 a provided on the clutchmember 361 engages with a clutch claw provided on the planet-sideinterlocking member 326, and thus the clutch member 361 is coupled tothe planet-side interlocking member 326 so as to be capable of in-unisonrotation. The clutch member 361 is caused to slide while maintaining thestate of being engaged with the sun gear 342 so as to be capable ofin-unison rotation by the engaging claw 361 b, and reaches the onposition while maintaining the engaged state with respect to the sungear 342. When the clutch member 361 switches to the off position, theengagement with the planet-side interlocking member 326 using the clutchclaw 361 a is canceled.

Accordingly, with the HST clutch 360, when the clutch member 361 isswitched to the on position, the sun gear 342 and the planet-sideinterlocking member 326 are interlocked so as to be capable of in-unisonrotation, and this achieves a state in which HST power transmission isset so that the motor shaft 333 a is interlocked with the output rotarymember 324 so as to be capable of in-unison rotation, thus enablingoutput from the continuously variable shift section 330 to be outputfrom the output rotary member 324. Also, when HST power transmission isset in the HST clutch 360, and when the sun gear 342 and the powertransmission shaft 323 are interlocked so as to be capable of in-unisonrotation, and the ring gear 344 and the planet-side interlocking member326 are interlocked so as to be capable of in-unison rotation, the sungear 342, the carrier 341, and the ring gear 344 can rotate in unisonwith the motor shaft 333 a such that autorotation of the planet gears343 does not occur.

The HST clutch 360 switches the sun gear 342 of the planetary powertransmission section 340 and the output rotary member 324 between theinterlocking-on state and the interlocking-off state while maintainingthe interlocked state between the ring gear 344 of the planetary powertransmission section 340 and the output rotary member 324.

When the clutch member 361 is switched to the off position, the HSTclutch 360 enters the state in which the setting of HST powertransmission is canceled so that the interlocking of the sun gear 342and the planet-side interlocking member 326 is cut off, the interlockingof the motor shaft 333 a with the output rotary member 324 is cut off,and a state is realized in which the ring gear 344 of the planetarypower transmission section 340 and the output rotary member 324 areinterlocked so as to be capable of in-unison rotation, thus enablingcombined drive force from the planetary power transmission section 340to be output from the output rotary member 324.

Accordingly, with the planetary power transmission section 340, when theHMT clutch 355 is switched to the state in which HST power transmissionis set, and the HST clutch 360 is switched to the state in which thesetting of HST power transmission is canceled, drive force transmittedfrom the engine to the input shaft 322 is inputted to the carrier 341via the power train 350, speed-changed drive force output from the motorshaft 333 a of the continuously variable shift section 330 is inputtedto the sun gear 342 via the power transmission shaft 323, drive forcefrom the engine and speed-changed drive force output from motor shaft333 a of the continuously variable shift section 330 are combined togenerate combined drive force, and the generated combined drive force isoutputted from the ring gear 344 to the output rotary member 324 via theplanet-side interlocking member 326 and the output-side interlockingmember 327.

In other words, the clutch mechanism 370 is configured to include theHMT clutch 355 and the HST clutch 360 in order to perform powertransmission setting for switching the setting of the shift powertransmission device 320 between HMT power transmission and HST powertransmission.

FIG. 49 is an illustrative diagram showing the relationship that theoperation states of the HMT clutch 355 and the HST clutch 360, theoperation state of the power transmission setting clutch mechanism 370,and the power transmission mode of the shift power transmission device320 have with each other. In FIG. 49, “OFF” indicates the off state ofthe HMT clutch 355 and the HST clutch 360, and “ON” indicates the onstate of the HMT clutch 355 and the HST clutch 360. As shown in thisfigure, when the HMT clutch 355 is switched to the off state and the HSTclutch 360 is switched to the on state, the power transmission settingclutch mechanism 370 enters the state in which HST power transmission isset, and the shift power transmission device 320 is set to HST powertransmission. When the HMT clutch 355 is switched to the on state, andthe HST clutch 360 is switched to the off state, the power transmissionsetting clutch mechanism 370 enters the state in which HMT powertransmission is set, and the shift power transmission device 320 is setto HMT power transmission.

FIG. 47 is a front view in vertical section of the shift powertransmission device 320 during HMT power transmission. As shown in thisfigure, in the shift power transmission device 320, when the HMT clutch355 is switched to the on state, and the HST clutch 360 is switched tothe off state, drive force from the input shaft 322 (drive force fromthe engine 308) is inputted to the carrier 341 of the planetary powertransmission section 340 via the power train 350, drive force input fromthe input shaft 322 is subjected to speed change by the continuouslyvariable shift section 330, the speed-changed drive force output fromthe motor shaft 333 a is inputted to the sun gear 342 of the planetarypower transmission section 340, the planetary power transmission section340 combines the drive force from the engine 308 that is inputted fromthe input shaft 322 with the speed-changed drive force input from thecontinuously variable shift section 330 so as to generate combined driveforce, and the combined drive force output from the ring gear 344 of theplanetary power transmission section 340 is transmitted to the endportion of the output rotary member 324 via the planet-side interlockingmember 326 and the output-side interlocking member 327, and output fromthe output rotary member 324 to the traveling transmission 313.

FIG. 48 is a front view in vertical section of the shift powertransmission device 320 during HST power transmission. As shown in thisfigure, in the shift power transmission device 320, when the HMT clutch355 is switched to the off state, and the HST clutch 360 is switched tothe on state, drive force input from the input shaft 322 is subjected tospeed change by the continuously variable shift section 330, and thespeed-changed drive force output from the motor shaft 333 a istransmitted to the end portion of the output rotary member 324 via thepower transmission shaft 323, the HST clutch 360, the planet-sideinterlocking member 326, and the output-side interlocking member 327,and output from the output rotary member 324 to the travelingtransmission 313.

When HST power transmission is set, the power transmission settingclutch mechanism 370 is in the state where power transmission from theinput shaft 322 to the carrier 341 of the planetary power transmissionsection 340 is cut off, the sun gear 342 is interlocked to the motorshaft 333 a via the power transmission shaft 323 so as to be capable ofin-unison rotation, and the ring gear 344 is interlocked to the motorshaft 333 a via the planet-side interlocking member 326, the clutchmember 361, the sun gear 342, and the power transmission shaft 323 so asto be capable of in-unison rotation. Accordingly, the sun gear 342, thecarrier 341, and the ring gear 344 of the planetary power transmissionsection 340 rotate in unison with the motor shaft 333 a, and in theshift power transmission device 320, during HST power transmission,output from the motor shaft 333 a of the continuously variable shiftsection 330 is transmitted to the output rotary member 324 withoutautorotation of the planet gears 343 occurring, that is to say, withoutrelative rotation of the sun gear 342 and the planet gears 343 occurringor relative rotation of the planet gears 343 and the ring gear 344occurring.

FIG. 50 is a graph (speed line diagram) showing output characteristicsof the shift power transmission device 320. A speed line indicating therotational speed of the output rotary member 324 is shown on thevertical axis in this graph. An operation position line L that passesthrough the position at which the rotational speed plotted on thevertical axis is zero “0”, and that indicates the position of the swashplate of the hydraulic pump 332 configuring the continuously variableshift section 330 is shown on the horizontal axis. Here, “n” on theoperation position line L indicates the neutral position of the swashplate 332 b at which the continuously variable shift section 330 is putinto the neutral state. Also, “a” on the operation position line L isthe set forward high-speed position, which is set as the maximum speedposition on the forward side of the swash plate 332 b, which is forswitching between the HST power transmission setting and the HMT powertransmission setting during no-load driving. Also, “+max” on theoperation position line L is the actual forward maximum speed positionof the continuously variable shift section 330, which is the swash plateangular position that is actually achieved by the swash plate 332 b ofthe hydraulic pump 332 when the continuously variable shift section 330is shifted to the operation limit on the forward high speed side. In asimple configuration in which rotation of the motor shaft 333 a isinputted to the planet terminal without being accelerated/decelerated,the set forward high-speed position “a” is set to a position in front ofthe actual forward maximum speed position “+max” in order to maintainspeed continuity at the point where there is a switch between HST powertransmission and HMT power transmission. Also, “−max” on the operationposition line L is the set reverse high-speed position, which is set asthe maximum speed position on the reverse side of the swash plate 332 b,which is operated in accordance with shift control. The set reversehigh-speed position “−max” is set to the same position as the swashplate angular position that is actually achieved by the swash plate 332b of the hydraulic pump 332 when the continuously variable shift section330 is shifted to the operation limit on the reverse high speed side.

A shift line S shown in FIG. 50 is an HST shift line (referred tohereinafter as the HST shift line S) that indicates change in therotational speed of the output rotary member 324 when the shift powertransmission device 320 is shifted during HST power transmission in thestate in which the accelerator of the engine 308 is set such that a setconstant speed of drive force is output, and a shift line M is an HMTshift line (referred to hereinafter as the HMT shift line M) thatindicates change in the rotational speed of the output rotary member 324when the shift power transmission device 320 is shifted during HMT powertransmission in the state in which the accelerator of the engine 308 isset such that a set constant speed of drive force is output.

As shown in FIG. 50, when the HMT clutch 355 is controlled so as to beswitched to the off state and the HST clutch 360 is controlled so as tobe switched to the on state, HST power transmission is set, and in thestate in which the HST power transmission setting is maintained, if thecontinuously variable shift section 330 is shifted from the neutralposition “n” toward the set forward high-speed position “a”, therotational speed of the output rotary member 324 steplessly increasesfrom zero “0” to the forward side along a forward range SF of the HSTshift line S, and when the continuously variable shift section 330reaches the set forward high-speed position “a”, the rotational speed ofthe output rotary member 324 reaches a first forward intermediate speed“V1”.

When the continuously variable shift section 330 reaches the set forwardhigh-speed position “a”, the HMT clutch 355 is controlled so as to beswitched from the off state to the on state, and the HST clutch 360 iscontrolled so as to be switched from the on state to the off state, thussetting HMT power transmission instead of HST power transmission, and inthe state in which the HMT power transmission setting is maintained, ifthe continuously variable shift section 330 is shifted from the setforward high-speed position “a” toward the neutral position “n”, therotational speed of the output rotary member 324 steples sly increasesfrom the first forward intermediate speed “V1” along a low speed rangeML of the HMT shift line M, and when the continuously variable shiftsection 330 reaches the neutral position “n”, the rotational speed ofthe output rotary member 324 reaches a second forward intermediate speed“V2”. In the state in which the HMT power transmission setting ismaintained, if the continuously variable shift section 330 is shiftedfrom the neutral position “n” toward the set reverse high-speed position“−max”, the rotational speed of the output rotary member 324 steplesslyincreases from the second forward intermediate speed “V2” along a highspeed range ML of the HMT shift line M, and when the continuouslyvariable shift section 330 reaches the set reverse high-speed position“−max”, the rotational speed of the output rotary member 324 reaches aforward maximum speed “V3”

In the state in which the HST power transmission setting is maintained,if the continuously variable shift section 330 is shifted from theneutral position “n” toward the set reverse high-speed position “−max”,the rotational speed of the output rotary member 324 steplesslyincreases from zero “0” to the reverse side along a reverse range SR ofthe HST shift line S, and when the continuously variable shift section330 reaches the set reverse high-speed position “−max”, the rotationalspeed of the output rotary member 324 reaches a reverse maximum speed“VR”.

The angle of inclination B of the HMT shift line M relative to theoperation position line L is set as follows in order for the drive forcethat is to be output in the shift state corresponding to the high speedrange MH of the HMT shift line M to be drive force with a rotationalspeed that is appropriate for location change traveling, in order forthe drive force that is to be output in the shift state corresponding tothe low speed range ML of the HMT shift line M to be drive force with arotational speed that is appropriate for task traveling, and in order toobtain speed-changed drive force with minimal loss that accompanies thespeed change of drive force input from the engine 308 when employing acontinuously variable shift section 330 whose hydraulic pump 332 has thesmallest possible discharge capacity.

A shift line extension line ME shown in FIG. 50 is an extension of theHMT shift line M toward the operation position line L, and a position“P” on the operation position line L is the intersection position wherethe shift line extension line ME and the operation position line Lintersect. Assuming that the swash plate 332 b of the hydraulic pump 332of the continuously variable shift section 330 can be tilted beyond theactual forward maximum speed position “+max”, which is the farthest tiltposition on the forward side that can actually be reached, to theintersection position “P”, letting “N” be the value of the virtual angleof inclination achieved by the swash plate 332 b when tilted to theintersection position “P”, and letting “X” be the value of the actualhighest swash plate angle that is actually achieved in the hydraulicpump 332 of the continuously variable shift section 330 when it isshifted to the actual forward maximum speed position “+max”, the angleof inclination B of the HMT shift line M relative to the operationposition line L is set to the angle of inclination that corresponds tothe case where N is two times the value of X (N/X=2.0). The settingcorresponding to N/X=2.0 depends on the setting of the dischargecapacity of the hydraulic pump 332 and the setting of the gear powertransmission ratio in the planetary power transmission section 340 andmechanical power transmission portions other than the planetary powertransmission section 340.

The angle of inclination B of the HMT shift line M relative to theoperation position line L is set to the angle of inclination at whichthe rotational speed of the output rotary member 324 at the forwardmaximum speed “V3” is greater than or equal to two times the rotationalspeed of the output rotary member 324 at the first forward intermediatespeed “V1”.

The setting corresponding to N/X=2.0 is based on the evidence describedbelow.

When the output rotation of the continuously variable shift section 330is zero and the output rotational speed is V2, all of the drive force isoutputted without passing through the continuously variable shiftsection 330. At the virtual swash plate angle position (P), at which theoutput rotation is zero, the drive force at the output rotational speedV2 passes through the continuously variable shift section 330 and isreturned to the drive side, and output becomes zero. In other words,mechanical transmission power that does not pass through thecontinuously variable shift section 330 and power from the continuouslyvariable shift section 330 (referred to hereinafter as HST power) canceleach other out. In actuality, the virtual swash plate angle position (P)is a virtual position, and therefore giving consideration to the factthat the actual maximum angle of inclination X=1 when the continuouslyvariable shift section 330 is at the actual forward maximum speedposition “+max”, since the rotational speed is 1/N, the HST power is 1/Ntimes the mechanical transmission power that does not pass through thecontinuously variable shift section 330.

Letting KM be the mechanical efficiency of mechanical transmissionpower, and letting KH be the power that passes through the continuouslyvariable shift section 330, the output power is a constant mechanicalpower ±HST power, and the overall efficiency achieved by the shift powertransmission device 320 is calculated as shown below.

When the continuously variable shift section 330 is at the neutralposition “n”:(1+0×1/N)/(1/KM+0×1/N/KH)=KM

When the continuously variable shift section 330 is at the set reversehigh-speed position “−max”:(1+1/N)/(1/KM+1/N/KH)=KM?KH(N+1)/(KM+KH?N)

When the continuously variable shift section 330 is at the actualforward maximum speed position “+max”:(1?1/N)/(1/KM?1/N?KH)=KM(N?1)/(N?KM?KH)

According to these calculations, the higher N is, the greater theefficiency can be improved.

FIG. 51 is an illustrative diagram showing the relationship betweenoverall efficiency and shift positions when varying the value N/X. Theoverall efficiency shown here was approximated as described above,assuming that KM=0.95 and KH=0.7, and using N/X=1.0, N/X=2.0, andN/X=3.0.

The horizontal axis shown in FIG. 51 indicates the shift position, andthe shift position on the horizontal axis is the ratio of the outputrotational speed when the continuously variable shift section 330 isshifted to an arbitrary shift position during forward-side HST powertransmission and HMT power transmission to the output rotational speedwhen the continuously variable shift section 330 is shifted to the setreverse high-speed position “−max”. In other words, letting Vn be therotational speed of drive force that is outputted when the continuouslyvariable shift section 330 is shifted to an arbitrary shift positionduring forward-side HST power transmission and HMT power transmission,Vn/V3 is the shift position on the horizontal axis. A vertical line Dshown in FIG. 51 is a line indicating the maximum speed during HST powertransmission when N/X=2.0, which is Vn/V3=0.33 (between 0.2 and 0.4). Avertical line E shown in FIG. 51 is a line indicating the speed when theswash plate of the hydraulic pump 332 is at the neutral position duringHMT power transmission when N/X=2.0, which is Vn/V3=0.67 (between 0.6and 0.8). Accordingly, the set forward high-speed position “a” of thecontinuously variable shift section 330 is a position between 0.2 and0.4 on the horizontal axis, and the neutral position “n” of the shift330 is a position between 0.6 and 0.8 on the horizontal axis.

An efficiency line K shown in FIG. 51 indicates the overall efficiencyof the continuously variable shift section 330. An efficiency line K1shown in FIG. 51 indicates the overall efficiency approximated usingN/X=1.0, an efficiency line K2 indicates the overall efficiencyapproximated using N/X=2.0, and an efficiency line K3 indicates theoverall efficiency approximated using N/X=3.0.

Between the vertical line D and the vertical line E, the overallefficiency is favorable when N/X=1.0, but since the output is also highon the high speed side, the amount of power loss increases, and even asmall difference in efficiency cannot be ignored. In consideration ofpower loss obtained by multiplying output power by the rate of loss,approximately N/X=1.8 is the minimum value. Although the mostappropriate value in terms of power loss has a wide range when the N/Xvalue is low around N/X=1.8, N/X=2.0 is the most appropriate value forreducing the size of the continuously variable shift section 330. If N/Xis approximately 1.5 to 2.5 in order to achieve balance, it is possibleto both realize higher efficiency in the high speed range and achieve a38% reduction in the size of the continuously variable shift section330. The output rotation of the planetary power transmission section 340during HMT power transmission at this time can also be designed so as tobe in a realistic range that does not exceed 10000 rpm. When the shiftpower transmission device 320 is an independent unit, lowering theextent of rotational speed from the drive source enables reducing theinfluence of torque loss caused by output portion sealing and the like,and therefore deceleration of 2.5 to 3 is performed by the planetarypower transmission section 340, which also makes the configurationrealistically more readily achievable. When employing the simple powertransmission setting clutch mechanism 370 as described above, thesetting of N/X=1.5 to 2.5 is advantageous in terms of high efficiencyand reducing the size of the continuously variable shift section 330.

FIG. 52 is an illustrative diagram showing the relationship between thevalue of N/X and size reduction of the continuously variable shiftsection 330. The horizontal axis in FIG. 52 indicates the value of N/X.A line F shown in FIG. 52 indicates the ratio “W” of the HST power (1/N)to the total power (1+1/N). The higher this ratio “W” is, the larger thedischarge capacity of the hydraulic pump 332 needs to be, and the largerthe continuously variable shift section 330 needs to be.

The size of the continuously variable shift section 330 can be madesmaller when drive force over a predetermined shift range is to beobtained by output from the planetary power transmission section 340than when it is to be obtained by output from the continuously variableshift section 330, and a line G shown in FIG. 52 indicates therelationship between the value of N/X and the extent to which the sizeof the continuously variable shift section 330 can be reduced.

Specifically, assuming that the actual maximum tilt position “+max” isthe point at which there is a switch between HST power transmission andHMT power transmission, the ratio of the maximum speed during HMT powertransmission (forward maximum speed “V3”) to the maximum speed duringHST power transmission is similarly calculated as (N+1)/(N?1)=Z. Z is5.0 when N/X=1.5, is 3.0 when N/X=2.0, is 2.3 when N/X=2.5, and is 2.0when N/X=3.0. The values indicated on the vertical axis in FIG. 52 arethe value of 1/Z.

The higher the value of Z is, the greater the shift range that can beobtained by HMT power transmission is, the smaller the shift range thatneeds to be obtained by HST power transmission is, and the greater thesize of the continuously variable shift section 330 can be reduced, butif the discharge capacity of the hydraulic pump 332 is too small, driveproblems will occur, such as the relief circuit opening and operating.Accordingly, by employing N/X=2.0, which achieves an intersectionbetween the line F and the line G, it is possible to obtain a shiftpower transmission device 320 capable of shift power transmission thatavoids the occurrence of drive problems in the continuously variableshift section 330, while also achieving a forward maximum speed “V3” anda second forward intermediate speed “V2” during HMT power transmissionthat are speeds necessary for location change and task, and alsoachieving a reduction in the size of the continuously variable shiftsection 330.

FIG. 53 is a block diagram showing a shift operation apparatus 371 thatperforms shift operations on the shift power transmission device 320. Asshown in this figure, the shift operation apparatus 371 includes acontrol apparatus 372 that is linked to a main shift operation section330 a and an auxiliary shift operation section 330 b of the continuouslyvariable shift section 330 and operation sections 355 a and 360 a of theHMT clutch 355 and the HST clutch 360, as well as a main shift operationdevice 377, an auxiliary shift operation device 385, an engine speedsensor 374, a swash plate angle sensor 375, an output speed sensor 376a, and an output speed sensor 376 b that are linked to the controlapparatus 372.

The main shift operation section 330 a performs shift operations on thehydraulic pump 332 by operating a main shift actuator 332 c for changingthe angle of the swash plate 332 b of the hydraulic pump 332 in thecontinuously variable shift section 330. The auxiliary shift operationsection 330 b performs shift operations on the hydraulic motor 333 byoperating an auxiliary shift actuator 333 c for changing the angle ofthe swash plate 333 b of the hydraulic motor 333 in the continuouslyvariable shift section 330. The main shift actuator 332 c and theauxiliary shift actuator 333 c are configured by a hydraulic cylinder,and the main shift operation section 330 a and the auxiliary shiftoperation section 330 b are configured by a hydraulic cylinder operationvalve. The operation section 355 a of the HMT clutch 355 is configuredby an operation valve that is connected to the hydraulic piston 358 viaan operation oil path formed inside the input shaft 322, and byoperating the hydraulic piston 358 so as to cause the clutch member 356to slide, the operation section 355 a switches the HMT clutch 355. Theoperation section 360 a of the HST clutch 360 is configured by anoperation valve that is connected to the oil chamber of the clutchmember 361 via an operation oil path formed inside the powertransmission shaft 323, and by supplying/discharging operation oilto/from the oil chamber of the clutch member 361, the operation section360 a causes the clutch member 361 to slide so as to switch the HSTclutch 360.

FIG. 54 is a plan view of operation positions of the main shiftoperation device 377. As shown in FIGS. 53 and 54, the main shiftoperation device 377 is configured by a shift lever provided in thedriving section 302 so as to be capable of being swung in the front/reardirection of the traveling body, and is swung to a neutral position“377N”, in a forward operation range “377F” that extends from theneutral position “377N” toward the front of the device body, and in areverse operation range “377W” that extends from the neutral position“377N” toward the rear of the device body. The shift operation device377 is linked to the control apparatus 372 via a shift detection sensor373 that detects the operation position of the shift operation device377. The shift detection sensor 373 is configured by a rotationpotential meter that is interlocked to the rotation operation shaft ofthe shift operation device 377, and when the shift operation device 377is swung, the shift detection sensor 373 operates, and a main shiftinstruction is outputted from the shift detection sensor 373 to thecontrol apparatus 372 in the form of an electrical signal.

The auxiliary shift operation device 385 is configured by a shift leverprovided in the driving section 302 so as to be capable of being swungin the front/rear direction of the traveling body, and is swung to a lowspeed position “L” and a high speed position “H”. The auxiliary shiftoperation device 385 is linked to the control apparatus 372 via anoperation position detection switch 386 that detects the operationposition of the auxiliary shift operation device 385. When the auxiliaryshift operation device 385 is moved to the low speed position “L”, theoperation position detection switch 386 is moved to the off side, and alow-speed auxiliary shift instruction is outputted from the operationposition detection switch 386 to the control apparatus 372 in the formof an electrical signal. When the auxiliary shift operation device 385is moved to the high speed position “H”, the operation positiondetection switch 386 is moved to the on side, and a high-speed auxiliaryshift instruction is outputted from the operation position detectionswitch 386 to the control apparatus 372 in the form of an electricalsignal.

The engine speed sensor 374 detects the rotational speed of the engine308, and outputs this detection result to the control apparatus 372. Theswash plate angle sensor 375 detects the angle of the swash plate of thehydraulic pump 332 of the continuously variable shift section 330, andoutputs this detection result to the control apparatus 372. The outputspeed sensor 376 a detects the rotational speed of the output rotarymember 324 as the output rotational speed of the shift powertransmission device 320, and outputs this detection result to thecontrol apparatus 372. The output speed sensor 376 b detects therotational speed of the motor shaft 333 a as the output rotational speedof the continuously variable shift section 330, and outputs thisdetection result to the control apparatus 372.

The control apparatus 372 is configured using a microcomputer, andincludes a shift control module 378, a restraint control module 381, ashift swash plate angle setting module 380, and a reference swash plateangle setting module 382.

The shift swash plate angle setting module 380 is configured by astorage section provided in the control apparatus 372. As shown in FIG.50, the shift swash plate angle setting module 380 receives a swashplate angle for performing control for switching the setting from HSTpower transmission to HMT power transmission, as a pre-set set shiftswash plate angle “c”. The set forward high-speed position “a” is set asthe set shift swash plate angle “c”.

The reference swash plate angle setting module 382 is configured by astorage section of the control apparatus 372. As shown in FIG. 50, aswash plate angle of the hydraulic pump 332 that is located a set angle“d” toward the low speed side from the set shift swash plate angle “c”is inputted in advance and set as a reference swash plate angle “e” inthe reference swash plate angle setting module 382.

Based on detection information from the engine speed sensor 374, theshift control module 378 detects the speed of the engine 308 whoseaccelerator has been set, performs shift control on the hydraulic pump332 and the hydraulic motor 333 based on this detection result, a mainshift instruction from the main shift operation device 377, an auxiliaryshift instruction from the auxiliary shift operation device 385,detection information from the swash plate angle sensor 375, anddetection information from the output speed sensor 376 a and the outputspeed sensor 376 b, and also controls the switching of the HST clutch360 and the HMT clutch 355 of the clutch mechanism 370.

The shift control module 378 compares the detected swash plate anglefrom the swash plate angle sensor 375 and the set shift swash plateangle “c” from the shift swash plate angle setting module 380, anddetermines whether or not the detected swash plate angle is equal to theset shift swash plate angle “c”, thus determining whether or not theswash plate angle sensor 375 detected a swash plate angle that is equalto the set shift swash plate angle “c”. In the case of determining thatthe swash plate angle sensor 375 detected a swash plate angle that isequal to the set shift swash plate angle “c”, the shift control module378 performs control for switching the HST clutch 360 of the clutchmechanism 370 to the off state, and performs control for switching theHMT clutch 355 to the on state, thus switching the setting from HSTpower transmission to HMT power transmission.

Upon receiving a low-speed auxiliary shift instruction from theauxiliary shift operation device 385, the shift control module 378performs a shift operation on the hydraulic pump 332 based on the mainshift instruction from the main shift operation device 377 and theauxiliary shift instruction from the auxiliary shift operation device385 such that the output speed of the output rotary member 324 of theshift power transmission device 320 is an output speed that correspondsto the main shift instruction from the main shift operation device 377,that is to say, such that the output speed of the output rotary member324 of the shift power transmission device 320 changes along the HSTshift line S and the HMT shift line M in accordance with the operationof the main shift operation device 377.

Upon receiving a high-speed auxiliary shift instruction from theauxiliary shift operation device 385, the shift control module 378performs a shift operation on the hydraulic pump 332 based on the mainshift instruction from the main shift operation device 377 and theauxiliary shift instruction from the auxiliary shift operation device385 such that the output speed of the output rotary member 324 of theshift power transmission device 320 is an output speed that is higherthan the output speed that corresponds to the main shift instructionfrom the main shift operation device 377.

The restraint control module 381 detects the power transmission state ofthe shift power transmission device 320 based on detection informationfrom the swash plate angle sensor 375, setting information regarding HSTpower transmission and HMT power transmission from the shift controlmodule 378, setting information from the reference swash plate anglesetting module 382, and setting information from the shift swash plateangle setting module 380, and switches between a restraint active stateand a restraint canceled state with respect to the shift control module378 based on the detection result.

When the shift power transmission device 320 is set to HST powertransmission, and the power transmission state is detected to be areverse power transmission state in which the combined drive force to beoutput is increased through a speed-increase shift operation in thereverse shift range of the continuously variable shift section 330 andin which the combined drive force to be output is decreased through aspeed-decrease shift operation in the reverse shift range of thecontinuously variable shift section 330, the restraint control module381 switches to the restraint canceled state with respect to the shiftcontrol module 378, and permits the shift control module 378 to performcontrol so as to move the auxiliary shift actuator 333 c to the highspeed side.

When the shift power transmission device 320 is set to HST powertransmission, and the power transmission state is detected to be a firstforward power transmission state in which the combined drive force to beoutput is increased through a speed-increase shift operation between theneutral position “n” and the reference swash plate angle “e” in theforward shift range of the continuously variable shift section 330 andin which the combined drive force to be output is decreased through aspeed-decrease shift operation between the neutral position “n” and thereference swash plate angle “e” in the forward shift range of thecontinuously variable shift section 330, the restraint control module381 switches to the restraint canceled state with respect to the shiftcontrol module 378, and permits the shift control module 378 to performcontrol so as to move the auxiliary shift actuator 333 c to the highspeed side.

When the shift power transmission device 320 is set to HST powertransmission, and the power transmission state is detected to be asecond forward power transmission state in which the combined driveforce to be output is increased through a speed-increase shift operationbetween the reference swash plate angle “e” and the set shift swashplate angle “c” in the forward shift range of the continuously variableshift section 330 and in which the combined drive force to be output isdecreased through a speed-decrease shift operation between the referenceswash plate angle “e” and the set shift swash plate angle “c” in theforward shift range of the continuously variable shift section 330, therestraint control module 381 switches to the restraint active state withrespect to the shift control module 378, and prohibits the shift controlmodule 378 from performing control so as to move the auxiliary shiftactuator 333 c to the high speed side.

When the shift power transmission device 320 is set to HMT powertransmission, and the power transmission state is detected to be a thirdforward power transmission state in which the combined drive force to beoutput is decreased through a speed-increase shift operation in theforward shift range of the continuously variable shift section 330 andin which the combined drive force to be output is increased through aspeed-decrease shift operation in the forward shift range of thecontinuously variable shift section 330, the restraint control module381 switches to the restraint active state with respect to the shiftcontrol module 378, and prohibits the shift control module 378 fromperforming control so as to move the auxiliary shift actuator 333 c tothe high speed side.

When the shift power transmission device 320 is set to HMT powertransmission, and the power transmission state is detected to be afourth forward power transmission state in which the combined driveforce to be output is increased through a speed-increase shift operationin the reverse shift range of the continuously variable shift section330 and in which the combined drive force to be output is decreasedthrough a speed-decrease shift operation in the reverse shift range ofthe continuously variable shift section 330, the restraint controlmodule 381 switches to the restraint canceled state with respect to theshift control module 378, and allows the shift control module 378 toperform control so as to move the auxiliary shift actuator 333 c to thehigh speed side.

In other words, when the output of the continuously variable shiftsection 330 and output of the planetary power transmission section 340are to be in the same rotation direction, the restraint control module381 causes auxiliary shifting to be performed by the hydraulic motor333. When the HMT power transmission speed range has multiple stages,the restraint control module 381 and the shift control module 378 areconfigured to function as described below. Specifically, after theauxiliary shift operation device 385 is switched from the low speedposition “L” to the high speed position “H”, if in the processing ofacceleration with the main shift operation device 377, there is a switchfrom a low-speed stage in the HMT power transmission speed range (n-thstage) to a high-speed stage in the HMT power transmission speed range((n+1)-th stage), the swash plate position that is to be switched to isin the vicinity of the intersection between the speed lines of the n-thauxiliary shift high speed range and the (n+1)-th auxiliary shift highspeed range. If the auxiliary shifting is switched at a pump swash plateposition that is tilted deeper than the intersection between theaforementioned speed lines, the motor swash plate is not tilted, and thepump swash plate is tilted by an amount that corresponds to theacceleration of the motor. When the output of the continuously variableshift section 330 and output of the planetary power transmission section340 are to be in opposite rotation directions, the restraint controlmodule 381 causes auxiliary shifting to be performed by the hydraulicpump 332, without auxiliary shifting being performed by the hydraulicmotor 333. If the swash plate neutral position of the continuouslyvariable shift section 330 will be exceeded as a result of tilting thepump swash plate, the motor auxiliary shifting is switched in thevicinity of the pump swash plate neutral position.

Upon receiving a high-speed auxiliary shift instruction from theauxiliary shift operation device 385 while the restraint control module381 is in the restraint active state, the shift control module 378performs control for shifting the hydraulic pump 332 to a higher speedbased on the main shift instruction and the high-speed auxiliary shiftinstruction such that the output speed of the shift power transmissiondevice 320 that corresponds to the main shift instruction increases inaccordance with the auxiliary shift instruction. Specifically, asindicated by arrow “I” in FIG. 50, the shift control module 378 performsauxiliary shift control for shifting the hydraulic pump 332 to a higherspeed such that the swash plate 332 b of the hydraulic pump 332 istilted to the swash plate angle position “a” that is displaced a setangle higher than the swash plate angle position “f” that corresponds tothe main shift instruction. Alternatively, as indicated by arrow “II” inFIG. 50, the shift control module 378 performs auxiliary shift controlfor shifting the hydraulic pump 332 to a lower speed such that the swashplate 332 b of the hydraulic pump 332 is tilted to the swash plate angleposition “h” that is displaced a set angle lower than the swash plateangle position “g” that corresponds to the main shift instruction. Theset angles in these cases are set as swash plate angles that correspondto the case where the shift power transmission device 320 is caused tooutput acceleration of the same or substantially same amount as theamount of acceleration of the output of the shift power transmissiondevice 320 that is achieved by auxiliary shift control for shifting thehydraulic motor 333 to a higher speed in accordance with a high-speedauxiliary shift instruction.

Accordingly, in the state in which the accelerator of the engine 308 isset such that drive force with a constant rotational speed is output,when the main shift operation device 377 is operated in the reverseoperation range “377R”, to the neutral position “377N”, and in theforward operation range “377F”, and the auxiliary shift operation device385 is switched to the low speed position “L” and the high speedposition “H”, the shift control module 378 performs control forswitching the setting of the shift power transmission device 320 betweenHST power transmission and HMT power transmission and performs shiftcontrol on the hydraulic pump 332 and the hydraulic motor 333, thuscausing the traveling body to travel in forward and reverse, as well astraveling while changing speed in forward and reverse, and stopping.

Specifically, if the main shift operation device 377 is moved to theneutral position “377N”, in the reverse operation range “377R”, or inthe low speed range portion “377FL” in the forward operation range“377F”, the shift power transmission device 320 is set to HST powertransmission due to the shift control module 378 performing control forswitching the HMT clutch 355 and the HST clutch 360 based on the mainshift instruction from the main shift operation device 377 and settinginformation from the shift swash plate angle setting module 380. If themain shift operation device 377 is moved to a mid-speed range portion“377FM” or a high speed range portion “377FH” in the forward operationrange “377F”, the shift power transmission device 320 is set to HMTpower transmission due to the shift control module 378 performingcontrol for switching the HMT clutch 355 and the HST clutch 360 based onthe main shift instruction from the main shift operation device 377 andsetting information from the shift swash plate angle setting module 380.

If the main shift operation device 377 is operated to the neutralposition “377N”, the shift control module 378 moves the swash plate 332b of the hydraulic pump 332 to the neutral position “n” based on themain shift instruction from the main shift operation device 377, thecontinuously variable shift section 330 enters the neutral state, andoutput from the shift power transmission device 320 is stopped.

If the main shift operation device 377 is moved in the low speed rangeportion “377FL” of the forward operation range “377F” while theauxiliary shift operation device 385 is at the low speed position “L”,the shift control module 378 tilts the swash plate 332 b of thehydraulic pump 332 on the forward side of the neutral position “n” basedon the main shift instruction from the main shift operation device 377,the low-speed auxiliary shift instruction from the auxiliary shiftoperation device 385, and detection information from the output speedsensor 376 a, and the speed of the drive force outputted by the shiftpower transmission device 320 changes along the forward range SF of theHST shift line S.

If the main shift operation device 377 is moved in the mid-speed rangeportion “377FM” and the high speed range portion “377FH” of the forwardoperation range “377F” while the auxiliary shift operation device 385 isat the low speed position “L”, the shift control module 378 tilts theswash plate 332 b of the hydraulic pump 332 over the forward side andthe reverse side based on the main shift instruction from the main shiftoperation device 377, the low-speed auxiliary shift instruction from theauxiliary shift operation device 385, and detection information from theoutput speed sensor 376 a, and the speed of the drive force outputted bythe shift power transmission device 320 changes along the low speedrange ML and the high speed range MH of the HMT shift line M.

When the main shift operation device 377 is moved in the low speed rangeportion “377FL” of the forward operation range “377F”, and when theauxiliary shift operation device 385 is at the high speed position “H”,if furthermore the shift control module 378 shifts the hydraulic pump332 between the neutral position “n” and the reference swash plate angle“e”, the restraint control module 381 enters the restraint canceledstate, the shift control module 378 performs an auxiliary shiftoperation for shifting the hydraulic motor 333 to a higher speed, andthe speed of the drive force outputted by the shift power transmissiondevice 320 changes along the forward range SAF of the auxiliary shiftingHST shift line SA.

When the main shift operation device 377 is moved in the low speed rangeportion “377FL” of the forward operation range “377F”, even when theauxiliary shift operation device 385 is at the high speed position “H”,if the shift control module 378 shifts the hydraulic pump 332 betweenthe neutral position “n” and the reference swash plate angle “e”, therestraint control module 381 is switched to the restraint active state,and the shift control module 378 does not perform auxiliary shiftcontrol for shifting the hydraulic motor 333 to a higher speed. In thiscase, as indicated by arrow “I” in FIG. 50, the shift control module 378performs shift control for shifting the hydraulic pump 332 to a higherspeed, the speed of the drive force outputted by the shift powertransmission device 320 changes along the forward range SF of the HSTshift line S so as to be drive force with a speed higher than the speedthat corresponds to the operation position of the main shift operationdevice 377 when the auxiliary shift operation device 385 is at the lowspeed position “L”.

When the main shift operation device 377 is moved to an operationposition in the low speed range portion “377FL” of the forward operationrange “377F”, and when the auxiliary shift operation device 385 isswitched from the low speed position “L” to the high speed position “H”,if the swash plate 332 b of the hydraulic pump 332 is positioned at aswash plate angle position between the neutral position “n” and thereference swash plate angle “e”, the restraint control module 381 is inthe restraint canceled state, the shift control module 378 performsauxiliary shift control for shifting the hydraulic motor 333 to a higherspeed, and the drive force output by the shift power transmission device320 becomes drive force at a speed that is on the line in the forwardrange SAF of the HST shift line SA for auxiliary shifting.

When the main shift operation device 377 is moved in the mid-speed rangeportion “377FM” of the forward operation range “377F”, even when theauxiliary shift operation device 385 is at the high speed position “H”,the restraint control module 381 is switched to the restraint activestate, and the shift control module 378 does not perform auxiliary shiftcontrol for shifting the hydraulic motor 333 to a higher speed. In thiscase, as indicated by arrow “II” in FIG. 50 for example, the shiftcontrol module 378 performs auxiliary shift control for shifting thehydraulic pump 332 to a higher speed, and the speed of the drive forceoutputted by the shift power transmission device 320 changes along thelow speed range ML of the HMT shift line M so as to be drive force at aspeed higher than the speed that corresponds to the operation positionof the main shift operation device 377 when the auxiliary shiftoperation device 385 is at the low speed position “L”.

When the main shift operation device 377 is moved to an operationposition in the mid-speed range portion “377FM” of the forward operationrange “377F”, even when the auxiliary shift operation device 385 isswitched from the low speed position “L” to the high speed position “H”,the restraint control module 381 is in the restraint active state, andthe shift control module 378 does not perform auxiliary shift controlfor shifting the hydraulic motor 333 to a higher speed. In this case, asindicated by arrow “II” in FIG. 50 for example, the shift control module378 performs auxiliary shift control for shifting the hydraulic pump 332to a higher speed, and the speed of the drive force outputted by theshift power transmission device 320 changes along the low speed range MLof the HMT shift line M so as to be drive force at a speed higher thanthe speed that corresponds to the operation position of the main shiftoperation device 377 when the auxiliary shift operation device 385 is atthe low speed position “L”.

When the main shift operation device 377 is moved in the high speedrange portion “377FH” of the forward operation range “377F”, and whenthe auxiliary shift operation device 385 is at the high speed position“H”, the restraint control module 381 enters the restraint canceledstate, the shift control module 378 performs an auxiliary shiftoperation for shifting the hydraulic motor 333 to a higher speed, andthe speed of the drive force outputted by the shift power transmissiondevice 320 changes along the HMT shift line MA for auxiliary shifting.

When the main shift operation device 377 is moved to an operationposition in the high speed range portion “377FH” of the forwardoperation range “377F”, and when the auxiliary shift operation device385 is switched from the low speed position “L” to the high speedposition “H”, the restraint control module 381 is in the restraintcanceled state, the shift control module 378 performs auxiliary shiftcontrol for shifting the hydraulic motor 333 to a higher speed, and thedrive force outputted by the shift power transmission device 320 becomesdrive force at a speed that is on the HMT shift line MA for auxiliaryshifting.

If the main shift operation device 277 is moved in the reverse operationrange “377R” while the auxiliary shift operation device 385 is at thelow speed position “L”, the shift control module 378 tilts the swashplate 332 b of the hydraulic pump 332 on the reverse side of the neutralposition “n” based on the main shift instruction from the main shiftoperation device 377, the low-speed auxiliary shift instruction from theauxiliary shift operation device 385, and detection information from theoutput speed sensor 376 a, and the speed of the drive force outputted bythe shift power transmission device 320 changes along the reverse rangeSR of the HST shift line S.

When the main shift operation device 377 is moved in the reverseoperation range “377R”, and when the auxiliary shift operation device385 is at the high speed position “H”, the restraint control module 381enters the restraint canceled state, the shift control module 378performs an auxiliary shift operation for shifting the hydraulic motor333 to a higher speed, and the speed of the drive force outputted by theshift power transmission device 320 changes along the reverse range SARof the HST shift line SA for auxiliary shifting.

When the main shift operation device 377 is moved to an operationposition in the reverse operation range “377R”, and when the auxiliaryshift operation device 385 is switched from the low speed position “L”to the high speed position “H”, the restraint control module 381 is inthe restraint canceled state, the shift control module 378 performsauxiliary shift control for shifting the hydraulic motor 333 to a higherspeed, and the drive force outputted by the shift power transmissiondevice 320 becomes drive force at a speed that is on the line in thereverse range SAR of the HST shift line SA for auxiliary shifting.

When a control target speed can be achieved by merely performing shiftcontrol on the hydraulic pump 332 in the shift range A shown in FIG. 50,even if a high-speed auxiliary shift instruction is received, only shiftcontrol of the hydraulic pump 332 is necessary, and the shift controlmodule 378 does not perform control for acceleration by performingauxiliary shift control on the hydraulic motor 333.

Alternative Embodiment

(1) Although the above-described embodiment gives the example where theHMT power transmission speed range has only one stage, an implementationis possible in which the HMT power transmission speed range has two ormore stages.

(2) Although the above-described embodiment gives the example where theclutch mechanism 370 is configured by a meshing type HMT clutch 355 andHST clutch 360, an implementation is possible in which the clutchmechanism 370 is configured by a friction HMT clutch 355 and HST clutch360.

INDUSTRIAL APPLICABILITY

The present invention is applicable to a combine, as well as anagricultural apparatus such as a rice planter, and various types ofvehicles such as a transport vehicle.

DESCRIPTION OF REFERENCE SIGNS First Embodiment

1 Travel apparatus

22 Input shaft

24 Output rotary member

30 Hydraulic continuously variable transmission

32 a Pump shaft

33 a Motor shaft

40 Planetary power transmission section

42 Sun gear

55 Input-side clutch mechanism

60 Output-side clutch mechanism

90 Charge pump

Second Embodiment

101 Travel apparatus

122 Input shaft

124 Output rotary member

130 Hydraulic continuously variable transmission

133 a Motor shaft

140 Planetary power transmission section

141 c Input gear

142 Sun gear

143 Planet gear

144 Ring gear

150 Forward/reverse switching mechanism

151 Forward power transmission gear

152 a Forward clutch member

153 Reverse power transmission shaft

154 Power transmission gear

155 Input gear

156 a Reverse clutch member

157 Reverse power transmission gear

160 Clutch mechanism

Third Embodiment

201 Travel apparatus

208 Engine

220 Shift power transmission device

230 Continuously variable shift section

232 Hydraulic pump

240 Planetary power transmission section

241 Carrier

242 Sun gear

244 Ring gear

270 Clutch mechanism

275 Swash plate angle sensor

277 Shift operation device

278 Shift control module

280 Shift swash plate angle setting module

a No-load swash plate angle

b Load swash plate angle

c Set shift swash plate angle

S HST shift line

M HMT shift line

SA1 Calculated HST shift line

MA1 Calculated HMT shift line

V In-unison rotation achievement speed

W Intersection

Fourth Embodiment

301 Travel apparatus

308 Engine

320 Shift power transmission device

330 Continuously variable shift section

332 Hydraulic pump

333 Hydraulic motor

340 Planetary power transmission section

370 Clutch mechanism

375 Swash plate angle sensor

377 Main shift operation device

378 Shift control module

381 Restraint control module

382 Reference swash plate angle setting module

c Set shift swash plate angle

e Reference swash plate angle

S HST shift line

What is claimed is:
 1. A travel power transmission apparatus comprising:a shift power transmission device including a hydrostatic continuouslyvariable shift section and a planetary power transmission section; thehydrostatic continuously variable shift section receiving drive forcefrom an engine and outputting the drive force after changing speed ofthe drive force along an HST shift line by the continuously variableshift section; and the planetary power transmission section receivingand combining the drive force from the engine and the speed-changeddrive force from the continuously variable shift section, and outputtingthe combined drive force after changing speed of the combined driveforce along an HMT shift line by the continuously variable shiftsection; the shift power transmission device further including a clutchmechanism switchable between an HST setting state in which HST powertransmission is set for outputting the speed-changed drive force fromthe continuously variable shift section to a travel apparatus, and anHMT setting state in which HMT power transmission is set for outputtingthe combined drive force from the planetary power transmission sectionis outputted to the travel apparatus; and a shift control module forperforming shift control on a hydraulic pump of the continuouslyvariable shift section and switch control on the clutch mechanism, basedon a shift instruction from a shift operation device, wherein the travelpower transmission apparatus further comprises: a swash plate anglesensor detecting a swash plate angle of the hydraulic pump; and a shiftswash plate angle setting module for setting, as a set shift swash plateangle of the hydraulic pump, the swash plate angle between a no-loadswash plate angle and a load swash plate angle, wherein the no-loadswash plate angle is achieved by the hydraulic pump in a shift state foroutputting speed-changed drive force at a speed corresponding to anin-unison rotation achievement speed at which the continuously variableshift section achieves in-unison rotation of a sun gear, a carrier and aring gear of the planetary power transmission section during the HSTpower transmission and no-load driving, and wherein the load swash plateangle is achieved by the hydraulic pump in a shift state for outputtingthe speed-changed drive force at a speed corresponding to the in-unisonrotation achievement speed of the continuously variable shift sectionduring the HST power transmission and set load driving; and wherein theshift control module is configured to control the clutch mechanism to beswitched from the HST setting state to the HMT setting state when theswash plate angle sensor detects the swash plate angle equal to the setshift swash plate angle.
 2. The travel power transmission apparatusaccording to claim 1, wherein the shift swash plate angle setting modulehas an adjustable configuration such that the setting of the set shiftswash plate angle can be changed.
 3. The travel power transmissionapparatus according to claim 1, wherein the shift swash plate anglesetting module is configured to: calculate and set a calculated HSTshift line for the HST power transmission and the load driving based ondetection information from the swash plate angle sensor, calculate andset a calculated HMT shift line corresponding to the calculated HSTshift line, determine the swash plate angle achieved by the hydraulicpump in a shift state in which the continuously variable shift sectionoutputs the speed-changed drive force at a speed corresponding to anintersection between the calculated HST shift line and the calculatedHMT shift line, and set the determined swash plate angle as the setshift swash plate angle.